One-Year Postoperative Patient-Reported Outcome Measures Are Associated With Three-Year to Five-Year Postoperative Satisfaction in Total Knee Arthroplasty

BACKGROUND

Over the past couple of decades, the definition of success after total knee arthroplasty (TKA) has shifted away from clinician-rated metrics and toward the patient's subjective experience. Therefore, understanding the aspects of patient recovery that drive 3-year to 5-year satisfaction after TKA is crucial. The aims of this study were to (1) determine the 1-year postoperative factors, specifically patient-reported outcome measures (PROMs) that were associated with 3-year and 5-year postoperative satisfaction and (2) understand the factors that drive those who are not satisfied at 1 year postoperatively to become satisfied later in the postoperative course.

METHODS

This was a retrospective study of 402 TKA patients who were gathered prospectively and presented for their 1-year follow-up. Demographics were collected preoperatively and patient-reported outcomes were collected at 1, 3, and 5 years postoperatively. Logistic regressions were used to identify the factors at 1 year that were associated with 3-year and 5-year satisfaction.

RESULTS

Associations between 1-year PROMs with 3-year satisfaction were observed. Longer term satisfaction at 5 years was more closely associated with EuroQol 5 Dimension Mobility, Activity Score, and Numerical Rating Scale Satisfaction. Of those who were not satisfied at 1 year, EuroQol 5 Dimension Mobility, Knee Disability Osteoarthritis Outcome Score Function in Sport and Recreation, and Satisfaction were associated with becoming satisfied at 3 years.

CONCLUSION

The 1-year PROMs were found to be associated with satisfaction at 3 to 5 years after TKA. Importantly, many of the PROMs that were associated with 3-year to 5-year satisfaction, especially in those who were not originally satisfied at 1 year, were focused on mobility and activity level.

A potential link between inflammatory profiles, clinical pain, pain catastrophizing and long-term outcomes after total knee arthroplasty surgery

BACKGROUND

Chronic postoperative pain after total knee replacement (TKR) is a major clinical problem. It is still unclear if specific inflammatory mediators are associated with long-term postoperative pain complications. The current exploratory study aimed to (1) evaluate a multiplex of inflammatory mediators 5 years after TKR surgery in patients with different degrees of postoperative pain intensities and (2) study any association of the markers with clinical pain intensity, cognitive and functional outcomes.

METHODS

Plasma samples were collected 5 years after TKR surgery from 76 knee patients (43 females; 33 males) and analysed for 44 inflammatory markers. Pain (using visual analogue scale, VAS), the pain catastrophizing scale (PCS) and the Oxford knee score (OKS) were evaluated. Patients were categorized as high or low groups based on VAS, PCS and OKS scores. Associations between inflammatory markers, VAS, PCS and OKS were analysed and the marker expressions were compared between groups.

RESULTS

Pearson's correlations found 12 biomarkers associated with VAS (p < 0.05), 4 biomarkers with PCS and 3 biomarkers with OKS (p < 0.05). Four markers were altered in patients suffering from high compared to low chronic postoperative pain, three markers were altered in high compared to low catastrophizers and three markers were altered in patients with poor functional scores (p < 0.05).

CONCLUSIONS

The present exploratory study suggests that low-grade inflammation might be present in a subset of patients with high pain, high catastrophizing and low function 5 years after TKR. These exploratory results provide insights into some of the long-term postoperative complications after TKR surgery.

SIGNIFICANCE STATEMENT

This exploratory study evaluated a subset of inflammatory markers and the association to clinical pain intensity, knee function and pain catastrophizing in patients 5 years after total knee replacement surgery. Our results provide insights into the understanding of the underlying mechanisms that may drive the long experience of pain after TKR surgery.

Use of a tourniquet is not associated with increased risk of venous thromboembolism after fast-track total knee arthroplasty: a prospective multicenter cohort study of 16,250 procedures

BACKGROUND AND PURPOSE

Venous thromboembolism (VTE) is a serious postoperative complication after total knee arthroplasty (TKA). Use of a tourniquet has shown conflicting results for risk of VTE after TKA. We aimed to investigate the associated risk of VTE after TKA using tourniquet in a fast-track set-up as no previous data exists.

PATIENTS AND METHODS

We performed an observational cohort study from 9 fast-track centers including unilateral primary TKA from 2010-2017 with prospective collection of preoperative risk-factors and complete 90-day follow-up. Use of a tourniquet was registered in the Danish Knee Arthroplasty Register. Postoperative VTE was identified from health records. We performed risk analyses using a mixed-effects logistic regression model adjusting for previously identified risk factors.

RESULTS

Of the 16,250 procedures (39% males, mean age 67.9 [SD 10.0] years, median LOS 2 [interquartile range 2-3]) 12,518 (77%) were performed with a tourniquet. The annual tourniquet usage varied greatly between departments from 0% to 100%, but also within departments from 0% to 99%. There was no significant difference between the 2 groups with 52 (0.42%) VTEs in the tourniquet group vs. 25 (0.67%) in the no-tourniquet group (p = 0.06 for cumulative 90-day incidence of VTE). This association remained statistically insignificant for VTE using tourniquet after adjustment for previously identified risk factors.

CONCLUSION

We found no association between the use of a tourniquet and increased risk of 90-day VTE after primary fast-track TKA, irrespective of the length of time for which the tourniquet was applied.

Accelerations Recorded by Simple Inertial Measurement Units with Low Sampling Frequency Can Differentiate between Individuals with and without Knee Osteoarthritis: Implications for Remote Health Care

Determining the presence and severity of knee osteoarthritis (OA) is a valuable application of inertial measurement units (IMUs) in the remote monitoring of patients. This study aimed to employ the Fourier representation of IMU signals to differentiate between individuals with and without knee OA. We included 27 patients with unilateral knee osteoarthritis (15 females) and 18 healthy controls (11 females). Gait acceleration signals were recorded during overground walking. We obtained the frequency features of the signals using the Fourier transform. The logistic LASSO regression was employed on the frequency domain features as well as the participant's age, sex, and BMI to distinguish between the acceleration data from individuals with and without knee OA. The model's accuracy was estimated by 10-fold cross-validation. The frequency contents of the signals were different between the two groups. The average accuracy of the classification model using the frequency features was 0.91 ± 0.01. The distribution of the selected features in the final model differed between patients with different severity of knee OA. In this study, we demonstrated that using logistic LASSO regression on the Fourier representation of acceleration signals can accurately determine the presence of knee OA.

The use of tourniquet in primary total knee arthroplasty does not increase the risk of venous thromboembolism within 90 days of surgery: a Danish nationwide cohort study of 19,804 patients

PURPOSE

Existing evidence estimates a twofold risk of venous thromboembolisms (VTEs) if tourniquet is applied during total knee arthroplasties (TKAs). However, this estimate relies on multiple trials with a low number of patients analyzing VTEs as a secondary outcome. We hypothesized that tourniquet-use increases the risk of symptomatic VTE within 90 days of contemporary primary TKA and aimed to use the extensive Danish healthcare registries to quantify this risk.

METHODS

Prospectively collected registry data from Danish patients receiving primary TKAs between 2014 and 2018 were included in the study. Patients were divided by tourniquet-use during surgery. By merging information from four nationwide registries, the study included 44 baseline characteristics with the potential to confound the association between tourniquet-use and VTE. Incidence rate and odds ratios were used to compare the risk of VTE within 90 days of surgery.

RESULTS

19,804 patients of whom 10,111 (51%) were operated with tourniquet and 9693 (49%) without were included. The mean age (SD) was 70 (9) in both groups and 62% were females in the tourniquet group compared with 61% in the no tourniquet group. The groups were similarly comparable across all other baseline characteristics except type of post-operative thromboprophylaxis, type of anaesthesia, implant fixation, and year of surgery. The 90-days incidence of VTE was 0.77% (95% CI 0.60-0.94) in the tourniquet group compared with 1.10% (95% CI 0.90-1.31) in the no tourniquet group. Following adjustment for the unbalanced confounders, the odds ratio for VTE was 0.77 (95% CI 0.54-1.10) associated with tourniquet-use.

CONCLUSION

In contemporary TKAs the rate of VTE within 90 days is low and not significant altered by tourniquet-use. Thus, tourniquet can safely be applied during primary TKA-surgery without jeopardizing the risk of postoperative VTE.

LEVEL OF EVIDENCE

II-prospective cohort study.

Patellofemoral Arthroplasty Results in Better Time-weighted Patient-reported Outcomes After 6 Years than TKA: A Randomized Controlled Trial

BACKGROUND

In a previous study, we reported the 2-year outcomes of a parallel-group, equivalence, randomized controlled trial (RCT; blinded for the first year) comparing patellofemoral arthroplasty (PFA) and TKA for isolated patellofemoral osteoarthritis (PF-OA). We found advantages of PFA over TKA for ROM and various aspects of knee-related quality of life (QOL) as assessed by patient-reported outcomes (PROs). Register data show increases in PFA revision rates from 2 to 6 years after surgery at a time when annual TKA revision rates are decreasing, which suggests rapidly deteriorating knee function in patients who have undergone PFA. We intended to examine whether the early advantages of PFA over TKA have deteriorated in our RCT and whether revision rates differ between the implant types in our study after 6 years of follow-up.

QUESTIONS/PURPOSES

(1) Does PRO improvement during the first 6 postoperative years differ between patients who have undergone PFA and TKA? (2) Does the PRO improvement at 3, 4, 5, and 6 years differ between patients who have undergone PFA and TKA? (3) Do patients who have undergone PFA have a better ROM after 5 years than patients who have had TKA? (4) Does PFA result in more revisions or reoperations than TKA during the first 6 postoperative years?

METHODS

We considered patients who had debilitating symptoms and PF-OA as eligible for this randomized trial. Screening initially identified 204 patients as potentially eligible; 7% (15) were found not to have sufficient symptoms, 21% (43) did not have isolated PF-OA, 21% (43) declined participation, and 1% (3) were not included after the target number of 100 patients had been reached. The included 100 patients were randomized 1:1 to PFA or TKA between 2007 and 2014. Of these, 9% (9 of 100) were lost before the 6-year follow-up; there were 12% (6 of 50) and 0% (0 of 50) deaths (p = 0.02) in the PFA and TKA groups, respectively, but no deaths could be attributed to the knee condition. There were no differences in baseline parameters for patients who had PFA and TKA, such as the proportion of women in each group (78% [39 of 50] versus 76% [38 of 50]; p > 0.99), mean age (64 ± 9 years versus 65 ± 9 years; p = 0.81) or BMI (28.0 ± 4.7 kg/m 2 versus 27.8 ± 4.1 kg/m 2 ; p = 0.83). Patients were seen for five clinical follow-up visits (the latest at 5 years) and completed 10 sets of questionnaires during the first 6 postoperative years. The primary outcome was SF-36 bodily pain. Other outcomes were reoperations, revisions, ROM, and PROs (SF-36 [eight dimensions, range 0 to 100 best, minimum clinically important difference {MCID} 6 to 7], Oxford Knee Score [OKS; one dimension, range 0 to 48 best, MCID 5], and Knee Injury and Osteoarthritis Outcome Score [KOOS; five dimensions, range 0 to 100 best, MCID 8 to 10]). Average PRO improvements over the 6 years were determined by calculating the area under the curve and dividing by the observation time, thereby obtaining a time-weighted average over the entire postoperative period. PRO improvements at individual postoperative times were compared for the patients who had PFA and TKA using paired t-tests. Range of movement changes from baseline were compared using paired t-tests. Reoperation and revision rates were compared for the two randomization groups using competing risk analysis.

RESULTS

Patients who underwent PFA had a larger improvement in the SF-36 bodily pain score during the first 6 years than those who underwent TKA (35 ± 19 vs. 23 ± 17; mean difference 12 [95% CI 4 to 20]; p = 0.004), and the same was true for SF-36 physical functioning (mean difference 11 [95% CI 3 to 18]; p = 0.008), KOOS Symptoms (mean difference 12 [95% CI 5 to 20]; p = 0.002), KOOS Sport/recreation (mean difference 8 [95% CI 0 to 17]; p = 0.048), and OKS (mean difference 5 [95% CI 2 to 8]; p = 0.002). No PRO dimension had an improvement in favor of TKA. At the 6-year time point, only the SF-36 vitality score differed between the groups being in favor of PFA (17 ± 19 versus 8 ± 21; mean difference 9 [95% CI 0 to 18]; p = 0.04), whereas other PRO measures did not differ between the groups. At 5 years, ROM had decreased less from baseline for patients who underwent PFA than those who had TKA (-4° ± 14° versus -11° ± 13°; mean difference 7° [95% CI 1° to 13°]; p = 0.02), but the clinical importance of this is unknown. Revision rates did not differ between patients who had PFA and TKA at 6 years with competing risk estimates of 0.10 (95% CI 0.04 to 0.20) and 0.04 (95% CI 0.01 to 0.12; p = 0.24), respectively, and also reoperation rates were no different at 0.10 (95% CI 0.04 to 0.20) and 0.12 (95% CI 0.05 to 0.23; p = 0.71), respectively.

CONCLUSION

Our RCT results show that the 2-year outcomes did not deteriorate during the subsequent 4 years. Patients who underwent PFA had a better QOL throughout the postoperative years based on several of the knee-specific outcome instruments. When evaluated by the 6-year observations alone and without considering earlier observations, we found no consistent difference for any outcome instruments, although SF-36 vitality was better for patients who underwent PFA. These combined findings show that the early advantages of PFA determined the results by 6 years. Our findings cannot explain the rapid deterioration of results implied by the high revision rates observed in implant registers, and it is necessary to question indications for the primary procedure and subsequent revision when PFA is in general use. Our data do not suggest that there is an inherent problem with the PFA implant type as otherwise suggested by registries. The long-term balance of advantages will be determined by the long-term QOL, but based on the first 6 postoperative years and ROM, PFA is still the preferable option for severe isolated PF-OA. A possible high revision rate in the PFA group beyond 6 years may outweigh the early advantage of PFA, but only detailed analyses of long-term studies can confirm this.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The Rosenberg view and coronal stress radiographs give similar measurements of articular cartilage height in knees with osteoarthritis

PURPOSE

Choosing the optimal radiographic methods to diagnose the cartilage height and degree of knee osteoarthritis is crucial to determine suitability for unicompartmental knee replacement. This study aims to evaluate and compare articular cartilage thickness measured using the Rosenberg view and coronal stress radiography. Intra- and interrater agreement and test-retest reliability of each method were determined. The hypothesis of the study was that the Rosenberg view and coronal stress radiographs provide similar assessments of articular cartilage height in the medial and lateral knee compartments of osteoarthritic knees.

METHODS

A prospective diagnostic study, including 73 patients was performed. Inclusion criteria were enrollment for either a medial unicompartmental or a total knee replacement. Radiographs were taken as the Rosenberg view, and coronal stress radiography using the Telos stress device. Repeated measurements were performed. Experienced knee surgeons performed measurements of cartilage height at a standardized location of joint space width (JSW), and a rater-perceived location of minimal joint space width (mJSW), thus allowing for reliability and agreement analysesusing weighted kappa. Coronal stress measurements were ultimately compared to the Rosenberg view using Spearman's rank correlation.

RESULTS

A total of 12,264 measurements were performed. The radiographic methods proved substantial reliability. Intra- and interrater agreement showed substantial to almost perfect agreement. A very strong correlation was observed in the medial knee compartment (r = 0.91; CI = 0.84-0.95; p < 0.001), with a mean difference of 0.1 mm and limits of agreement of - 1.5 to 1.7 mm, when comparing JSW between the Rosenberg view and varus stress. Only a strong correlation was observed medially when using mJSW, and when using this measurementmore incidences of bone-on-bone were observed than when measuring with JSW. A Strong correlation was observed in the lateral knee compartment (r = 0.83; CI = 0.71-0.89; p < 0.001), with a mean difference of 0.62 mm and limits of agreement of - 1.5 to 2.7 mm, when comparing JSW between the Rosenberg view and valgus stress.

CONCLUSION

The Rosenberg view is similar to 20° coronal valgus-varus stress radiography for determining articular cartilage thickness. Both techniques can be used in a clinical setting. Therefore, extra radiographs, equipment and expertise could be saved, when solely utilizing the Rosenberg view which is simple to perform.

LEVEL OF EVIDENCE

III.

Criterion Validity of Linear Accelerations Measured with Low-Sampling-Frequency Accelerometers during Overground Walking in Elderly Patients with Knee Osteoarthritis

Sensors with a higher sampling rate produce higher-quality data. However, for more extended periods of data acquisition, as in the continuous monitoring of patients, the handling of the generated big data becomes increasingly complicated. This study aimed to determine the validity and reliability of low-sampling-frequency accelerometer (SENS) measurements in patients with knee osteoarthritis. Data were collected simultaneously using SENS and a previously validated sensor (Xsens) during two repetitions of overground walking. The processed acceleration signals were compared with respect to different coordinate axes to determine the test-retest reliability and the agreement between the two systems in the time and frequency domains. In total, 44 participants were included. With respect to different axes, the interclass correlation coefficient for the repeatability of SENS measurements was [0.93-0.96]. The concordance correlation coefficients for the two systems' agreement were [0.81-0.91] in the time domain and [0.43-0.99] in the frequency domain. The absolute biases estimated by the Bland-Altman method were [0.0005-0.008] in the time domain and [0-0.008] in the frequency domain. Low-sampling-frequency accelerometers can provide relatively valid data for measuring the gait accelerations in patients with knee osteoarthritis and can be used in the future for remote patient monitoring.

Monitoring of Campylobacter jejuni in a chicken infection model by measuring specific volatile organic compounds and by qPCR

Campylobacter is one of the leading bacterial foodborne pathogens worldwide. Poultry is the host species with this pathogen with the highest clinical impact. Flocks become colonised with Campylobacter, which leads to contamination of product entering the food-chain. Rapid and reliable Campylobacter detection methods could support controls to minimize the risks of contamination within the food-chain, which would easier enable the implementation of a logistical slaughter schedule or other control options. The present study evaluates current and emerging C. jejuni detection technologies on air samples in a unique study set-up of pre-defined C. jejuni prevalences. Both non-invasive detection technologies on air samples by subsequent measuring of volatile organic compounds (VOCs) or by qPCR detected the C. jejuni presence and could additionally distinguish between the number of present C. jejuni-positive birds in the study set-up. Nevertheless, electrostatic air samplers diagnosed fewer birds as C. jejuni-positive compared to the cultivation-based method. By measuring the VOCs, it was possible to detect the presence of two positive birds in the room. This apparent high sensitivity still needs to be verified in field studies. Techniques, such as these promising methods, that can facilitate C. jejuni surveillance in poultry flocks are desirable to reduce the risk of infection for humans.

The Role of Nuclear Medicine Imaging with 18F-FDG PET/CT, Combined 111In-WBC/99mTc-Nanocoll, and 99mTc-HDP SPECT/CT in the Evaluation of Patients with Chronic Problems after TKA or THA in a Prospective Study

Background: The aim of this prospective study was to assess the diagnostic value of nuclear imaging with ¹⁸F-FDG PET/CT (FDG PET/CT), combined ¹¹¹In-WBC/^99mTc-Nanocoll, and ^99mTc-HDP SPECT/CT (dual-isotope WBC/bone marrow scan) for patients with chronic problems related to knee or hip prostheses (TKA or THA) scheduled by a structured multidisciplinary algorithm. Materials and Methods: Fifty-five patients underwent imaging with ^99mTc–HDP SPECT/CT (bone scan), dual-isotope WBC/bone marrow scan, and FDG PET/CT. The final diagnosis of prosthetic joint infection (PJI) and/or loosening was based on the intraoperative findings and microbiological culture results and the clinical follow-up. Results: The diagnostic performance of dual-isotope WBC/bone marrow SPECT/CT for PJI showed a sensitivity of 100% (CI 0.74–1.00), a specificity of 97% (CI 0.82–1.00), and an accuracy of 98% (CI 0.88–1.00); for PET/CT, the sensitivity, specificity, and accuracy were 100% (CI 0.74–1.00), 71% (CI 0.56–0.90), and 79% (CI 0.68–0.93), respectively. Conclusions: In a standardized prospectively scheduled patient group, the results showed highly specific performance of combined dual-isotope WBC/bone marrow SPECT/CT in confirming chronic PJI. FDG PET/CT has an appropriate accuracy, but the utility of its use in the clinical diagnostic algorithm of suspected PJI needs further evidence.

A mechanism-based proof of concept study on the effects of duloxetine in patients with painful knee osteoarthritis

BACKGROUND

The global burden of osteoarthritis (OA) is steadily increasing due to demographic and lifestyle changes. The nervous system can undergo peripheral and central neuroplastic changes (sensitization) in patients with OA impacting the options to manage the pain adequately. As a result of sensitization, patients with OA show lower pressure pain thresholds (PPTs), facilitated temporal summation of pain (TSP), and impaired conditioned pain modulation (CPM). As traditional analgesics (acetaminophen and non-steroidal anti-inflammatory drugs) are not recommended for long-term use in OA, more fundamental knowledge related to other possible management regimes are needed. Duloxetine is a serotonin-noradrenalin reuptake inhibitor, and analgesic effects are documented in patients with OA although the underlying fundamental mechanisms remain unclear. The descending pain inhibitory control system is believed to be dependent on serotonin and noradrenalin. We hypothesized that the analgesic effect of duloxetine could act through these pathways and consequently indirectly reduce pain and sensitization. The aim of this mechanistic study is to investigate if PPTs, TSP, CPM, and clinical pain parameters are modulated by duloxetine.

METHODS

This proof of concept study is a randomized, placebo-controlled, double-blinded, crossover trial, which compares PPTs, TSP, and CPM before and after 18 weeks of duloxetine and placebo in forty patients with knee OA. The intervention periods include a titration period (2 weeks), treatment period (60 mg daily for 14 weeks), and a discontinuation period (2 weeks). Intervention periods are separated by 2 weeks.

DISCUSSION

Duloxetine is recommended for the treatment of chronic pain, but the underlying mechanisms of the analgesic effects are currently unknown. This study will investigate if duloxetine can modify central pain mechanisms and thereby provide insights into the underlying mechanisms of the analgesic effect.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04224584 . Registered on January 6, 2020. EudraCT 2019-003437-42 . Registered on October 22, 2019. The North Denmark Region Committee on Health Research Ethics N-20190055. Registered on October 31, 2019.

MRi of the knee compared to specialized radiography for measurements of articular cartilage height in knees with osteoarthritis

This study aims to evaluate and compare extremity-MRi with specialized radiography by measuring articular cartilage height in patients with knee osteoarthritis. A prospective study, including sixty patients. Measurements on MRi images, Rosenberg view, and coronal stress radiographs were performed. MRI was compared to specialized radiography. Measurements in the medial compartment showed negligible/weak correlation between MRi and Rosenber/varus stress. In the lateral compartment, MRi and the Rosenberg/valgus stress view were strongly correlated. We conclude that MRi cannot replace radiographs for the measurement of articular cartilage thickness. MRi should, however, be reserved for more unusual cases of atypical clinical findings.

Reduced survival of total knee arthroplasty after previous unicompartmental knee arthroplasty compared with previous high tibial osteotomy: a propensity-score weighted mid-term cohort study based on 2,133 observations from the Danish Knee Arthroplasty Registry

Background and purpose - Both medial unicompartmental knee arthroplasties (UKA) and high tibial osteotomies (HTO) are reliable treatments for isolated medial knee osteoarthritis. However, both may with time need conversion to a total knee arthroplasty (TKA). We conducted the largest nationwide registry comparison of the survival of TKA following UKA with TKA following HTO.Patients and methods - From the Danish Knee Arthroplasty Registry, aseptic conversions to TKA from UKA and TKA converted from HTO within the period of 1997-2018 were retrieved. The Kaplan-Meier method and the Cox proportional hazards regression were used to estimate the survival and hazard ratio (HR) for revision, considering confounding by indication utilizing propensity-score based inverse probability of treatment weighting (PS-IPTW).Results - PS-IPTW yielded a well-balanced pseudo-cohort (standard mean difference (SMD) < 0.1 for all covariates, except implant supplementation) of 963.8 TKAs following UKA and 1139.1 TKAs following HTO. The survival of TKA following UKA was significantly less than that of TKA following HTO with a 5-year estimated survival of 0.88 (95% confidence interval (CI) 0.85-0.90) and 0.94 (CI 0.93-0.96), respectively. The differences in survival corresponded to an implant-supplementation adjusted HR of 2.7 (CI 2.4-3.1) for TKA following UKA compared with TKA following HTO.Interpretation - Previous UKA more than doubled the revision risk of a subsequent TKA compared with previous HTO. This potential risk should be considered in the shared treatment decision of patients who are candidates for both UKA and HTO.

Multidisciplinary Diagnostic Algorithm for Evaluation of Patients Presenting with a Prosthetic Problem in the Hip or Knee: A Prospective Study

The predominant indications for revision surgery after total hip (THA) or knee arthroplasty (TKA) are an aseptic failure (AF) and prosthetic joint infection (PJI). Accurate diagnosis is crucial. Therefore, we evaluated prospectively a multidisciplinary diagnostic algorithm including multi-modal radionucleid imaging (RNI) and extended microbiological diagnostics. If the surgeon suspected PJI or AF, revision surgery was performed with multiple samples obtained in parallel for special culture procedures and later molecular analyses. Alternatively, if the underlying cause was not evident, RNI was scheduled comprising ⁹⁹Tc—HDP SPECT/CT, ¹¹¹In-labeled white blood cells combined with ⁹⁹Tc-nanocoll bone marrow SPECT/CT, and ¹⁸F-FDG PET/CT. A multidisciplinary clinical team made a recommendation on the indication for a diagnostic procedure guided by RNI images or revision surgery. A total of 156 patients with 163 arthroplasties were included. Fifty-five patients underwent RNI. In all, 118 revision surgeries were performed in 112 patients: 71 on the indication of AF and 41 revision of PJI. Thirty-four patients were concluded with chronic pain, and revision surgery refrained. The effective median follow-up period was 13 months. A structured approach offered by the algorithm was useful for the clinician in the evaluation of patients with a failing TKA or THA. Surgical revision was possibly obviated in approximately 20% of patients where an explanation or cause of failure was not found. The algorithm served as an effective tool.

72 revision surgeries for aseptic failure after hip or knee arthroplasty: a prospective study with an extended diagnostic algorithm

BACKGROUND

Unrecognized periprosthetic joint infections are a concern in revision surgery for aseptic failure (AF) after total hip (THA) or knee (TKA) arthroplasties. A gold diagnostic standard does not exist. The aim of the current study was to determine the prevalence of unrecognized periprosthetic joint infection (PJI) in a cohort of revision for AF, using an experimental diagnostic algorithm.

METHODS

The surgeons' suspicion of AF was based primarily on patient history and clinical evaluation. X-ray imaging was used to reveal mechanical problems. To rule out an infectious aetiology standard blood biochemical tests were ordered in most patients. Evaluation followed the existing practice in the institute. Cases were included if revision surgery was planned for suspected AF. Intraoperatively, five synovial tissue biopsies were obtained routinely. PJI was defined as ≥3 positive cultures with the same microorganism(s). Patients were followed for 1 year postoperatively. Protocol samples included joint fluid, additional synovial tissue biopsies, bone biopsy, swabs from the implant surface, and sonication of retrieved components. Routine and protocol samples were cultured with extended incubation (14 days) and preserved for batchwise 16S rRNA gene amplification. Patients were stratified based on culture results and a clinical status was obtained at study end.

RESULTS

A total of 72 revisions were performed on 71 patients (35 THA and 37 TKA). We found five of 72 cases of unrecognized PJI. Extended culture and protocol samples accounted for two of these. One patient diagnosed with AF was treated for a PJI during follow-up. The remaining patients did not change status from AF during follow-up.

CONCLUSIONS

We found a low prevalence of unrecognized periprosthetic joint infections in patients with an AF diagnosis. The algorithm strengthens the surgeons' preoperative diagnosis of a non-infective condition. Evaluation for a failing TKA or THA is complex. Distinguishing between AF and PJI pre-operatively was a clinical decision. Our data did not support additional testing in routine revision surgery for AF.

Revision Risk for Total Knee Arthroplasty Converted from Medial Unicompartmental Knee Arthroplasty: Comparison with Primary and Revision Arthroplasties, Based on Mid-Term Results from the Danish Knee Arthroplasty Registry

BACKGROUND

Medial unicompartmental knee arthroplasties (UKAs) have good clinical outcomes but implant survival is inferior to that of total knee arthroplasties (TKAs). Conversion to a TKA is a reliable option when UKA fails. However, there is controversy regarding these conversions. The aim of this study was to analyze the survival of TKAs converted from UKAs when compared with both primary and revision TKAs.

METHODS

On the basis of registrations in the Danish Knee Arthroplasty Registry from 1997 to 2017, 1,012 TKAs converted from UKAs were compared with 73,819 primary TKAs and 2,572 revision TKAs. The primary outcome was the risk of revision. Secondarily, the study analyzed the influence of different implants, the indication for the UKA conversion, and surgical volume on the survival of TKA converted from UKA. Third, the study compared the indications for revision.

RESULTS

The converted UKAs were mainly mobile-bearing (85%) and, at the time of conversion, the patients were younger (mean [standard deviation], 66 ± 10 years) and more were Charnley class A (55%) compared with patients with primary TKA (70 ± 9 years and 35% class A) or revision TKA (70 ± 10 years and 42% class A) (all p < 0.001). The survival of TKAs converted from UKAs was comparable with that of revision TKAs (p = 0.42) and significantly inferior to the survival of primary TKAs (p < 0.001). This relationship was unaffected by differences between the groups, with an adjusted hazard ratio of 0.94 (95% confidence interval [CI]: 0.74 to 1.19) compared with revision TKAs and 3.00 (95% CI: 2.47 to 3.66) compared with primary TKAs. The survival of TKA converted from UKA was unaffected by differences in the conversion implants (all p ≥ 0.47), experience with revision surgery (all p ≥ 0.06), and the indications for the UKA-to-TKA conversion (all p ≥ 0.27). Instability (26%) and unexplained pain (13%) were more frequent indications for revisions of TKA converted from UKA (p < 0.001).

CONCLUSIONS

TKA converted from medial UKA has a 3-fold higher risk of revision when compared with primary TKA. The implant survival resembled that of revision TKA but with a higher prevalence of unexplained pain and instability.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Randomized clinical trial of medial unicompartmentel versus total knee arthroplasty for anteromedial tibio-femoral osteoarthritis. The study-protocol

BACKGROUND

In treatment of isolated medial unicondylar osteoarthritis of the knee, it is possible to choose between medial unicondylar knee arthroplasty (mUKA), or a total knee prosthesis (TKA). The demand for a blinded multicenter RCT with the comparison of mUKA and TKA has been increasing in recent years, to determine which prosthesis is better. Supporters of TKA suggest this treatment gives a more predictable and better result, whereas supporters of UKA suggest it is unnecessary to remove functional cartilage in other compartments. If the mUKA is worn or loosens, revision surgery will be relatively easy, whereas revision-surgery after a TKA can be more problematic.

METHODS

A double-blinded multicenter Randomized Clinical Trial setup is the aim of the study. 6 hospitals throughout all 5 municipal regions of Denmark will be participating in the study. 350 patients will be included prospectively. Follow-up will be with PROM-questionnaires and clinical controls up to 20 years.

DISCUSSION

Results will be assessed in terms of 1) PROM-questionnaires, 2) Clinical assessment of knee condition, 3) cost analysis. To avoid bias, all participants except the theatre-staff will be blinded.

PROMS

OKS, KOOS, SF36, Forgotten Joint Score, EQ5D, UCLA activity scale, Copenhagen Knee ROM scale, and Anchor questions. Publications are planned at 2, 5 and 10 years after inclusion of the last patient. The development of variables over time will be analyzed by calculating the area under the curve (AUC) for the variable relative to the initial value, and comparisons of the between-group differences will be based on parametric statistics. In this study, we feel that we have designed a study that will address these concerns with a well-designed double-blinded multicentre RCT.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03396640 . Initial Release: 09/19/2017. Date of enrolment of first participant: 10/11/17.

Relationship between outcome scores and knee laxity following total knee arthroplasty: a systematic review

Background and purpose - Instability following primary total knee arthroplasty (TKA) is, according to all national registries, one of the major failure mechanisms leading to revision surgery. However, the range of soft-tissue laxity that favors both pain relief and optimal knee function following TKA remains unclear. We reviewed current evidence on the relationship between instrumented knee laxity measured postoperatively and outcome scores following primary TKA. Patients and methods - We conducted a systematic search of PubMed, Embase, and Cochrane databases to identify relevant studies, which were cross-referenced using Web of Science. Results - 14 eligible studies were identified; all were methodologically similar. Both sagittal and coronal laxity measurement were reported; 6 studies reported on measurement in both extension and flexion. In knee extension from 0° to 30° none of 11 studies could establish statistically significant association between laxity and outcome scores. In flexion from 60° to 90° 6 of 9 studies found statistically significant association. Favorable results were reported for posterior cruciate retaining (CR) knees with sagittal laxity between 5 and 10 mm at 75-80° and for knees with medial coronal laxity below 4° in 80-90° of flexion. Interpretation - In order to improve outcome following TKA careful measuring and adjusting of ligament laxity intraoperatively seems important. Future studies using newer outcome scores supplemented by performance-based scores may complement current evidence.

Prior High Tibial Osteotomy Does Not Affect the Survival of Total Knee Arthroplasties: Results From the Danish Knee Arthroplasty Registry

BACKGROUND

High tibial osteotomy (HTO) is a joint preserving treatment of unicompartmental osteoarthritis in the knee. In cases with insufficient or deteriorating clinical results patients may undergo a total knee arthroplasty (TKA). The influence of prior HTO on TKA survival is debated.

METHODS

We conducted a population-based registry study comparing 1044 primary TKAs in patients with prior HTO to 63,763 de novo TKAs inserted from 1997 to 2015. Implant survival was estimated by Kaplan-Meier analysis with revision of any kind as endpoint. Patient and surgery characteristics, including choice of implant design, were compared and their influence on TKA survival was estimated by Cox regression. Finally, indications of revision were compared between the groups.

RESULTS

TKA following HTO had an inferior survival with a 10-year estimated survival of 91% compared to 94% for de novo TKA, corresponding to a crude hazard ratio (HR) of 1.73 (P < .001). However, after adjustment for differences in gender and age this risk diminished (HR 1.19, P = .09). The choice of implant constraint was similar between the groups and in both groups posterior stabilized TKA was associated with inferior survival with an adjusted HR of 1.46 (P = .03) in post-HTO TKA when compared to cruciate-retaining TKA.

CONCLUSION

TKA following HTO had a crude inferior survival when compared to TKA without prior surgery of any kind. The inferior survival was explainable by patient characteristics, defined by male gender and lower age, rather than the prior HTO. However, when the prior HTO resulted in the use of posterior stabilized TKA the survival decreased.

The Mark Coventry Award: Patellofemoral Arthroplasty Results in Better Range of Movement and Early Patient-reported Outcomes Than TKA

BACKGROUND

Controversy exists over the surgical treatment for severe patellofemoral osteoarthritis. We therefore wished to compare the outcome of patellofemoral arthroplasty (PFA) with TKA in a blinded randomized controlled trial.

QUESTIONS/PURPOSES

In the first 2 years after surgery: (1) Does the overall gain in quality of life differ between the implants based on the area under the curve of patient-reported outcomes (PROs) versus time? (2) Do patients obtain a better quality of life at specific points in time after PFA than after TKA? (3) Do patients get a better range of movement after PFA than after TKA? (4) Does PFA result in more complications than TKA?

METHODS

Patients were eligible if they had debilitating symptoms and isolated patellofemoral disease. One hundred patients were included from 2007 to 2014 and were randomized to PFA or TKA (blinded for the first year; blinded to patient, therapists, primary care physicians, etc; quasiblinded to assessor). Patients were seen for four clinical followups and completed six sets of questionnaires during the first 2 postoperative years. SF-36 bodily pain was the primary outcome. Other outcomes were range of movement, PROs (SF-36, Oxford Knee Score [OKS], Knee injury and Osteoarthritis Outcome Score [KOOS]) as well as complications and revisions. Four percent (two of 50) of patients died within the first 2 years in the PFA group (none in the TKA group), and 2% (one of 50) became ill and declined further participation after 1 year in the PFA group (none in the TKA group). The mean age at inclusion was 64 years (SD 8.9), and 77% (77 of 100) were women.

RESULTS

The area under the curve (AUC) up to 2 years for SF-36 bodily pain of patients undergoing PFA and those undergoing TKA was 9.2 (SD 4.3) and 6.5 (SD 4.5) months, respectively (p = 0.008). The SF-36 physical functioning, KOOS symptoms, and OKS also showed a better AUC up to 2 years for PFA compared with TKA (6.6 [SD 4.8] versus 4.2 [SD 4.3] months, p = 0.028; 5.6 [SD 4.1] versus 2.8 [SD 4.5] months, p = 0.006; 7.5 [SD 2.7] versus 5.0 [SD 3.6] months, p = 0.001; respectively). The SF-36 bodily pain improvement at 6 months for patients undergoing PFA and those undergoing TKA was 38 (SD 24) and 27 (SD 23), respectively (p = 0.041), and at 2 years, the improvement was 39 (SD 24) and 33 (SD 22), respectively (p = 0.199). The KOOS symptoms improvement at 6 months for patients undergoing PFA and those undergoing TKA was 24 (SD 20) and 7 (SD 21), respectively (p < 0.001), and at 2 years, the improvement was 27 (SD 19) and 17 (SD 21), respectively (p = 0.023). Improvements from baseline for KOOS pain, SF-36 physical functioning, and OKS also differed in favor of PFA at 6 months, whereas only KOOS symptoms showed a difference between the groups at 2 years. No PRO dimension showed a difference in favor of TKA. At 4 months, 1 year, and 2 years, the ROM change from baseline for patients undergoing PFA and those undergoing TKA was (-7° [SD 13°] versus -18° [SD 14°], p < 0.001; -4° [SD 15°] versus -11° [SD 12°], p = 0.011; and -3° [SD 12°] versus -10° [SD 12°], p = 0.010). There was no difference in the number of complications. During the first 2 postoperative years, there were two revisions in patients undergoing PFA (one to a new PFA and one to a TKA).

CONCLUSIONS

Patients undergoing PFA obtain a better overall knee-specific quality of life than patients undergoing TKA throughout the first 2 years after operation for isolated patellofemoral osteoarthritis. At 2 years, only KOOS function differs between patients undergoing PFA and those undergoing TKA, whereas other PRO dimensions do not show a difference between groups. The observations can be explained by patients undergoing PFA recovering faster than patients undergoing TKA and the functional outcome being better for patients undergoing PFA up to 9 months. Patients undergoing PFA regain their preoperative ROM, whereas patients undergoing TKA at 2 years have lost 10° of ROM. We found no differences in complications.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Immunoassays for diagnosis of coagulation disorders

Immunoassays play a pivotal role in the clinical laboratory. In the coagulation section of the laboratory, they are used as an aid for diagnosis of deep vein thrombosis or pulmonary embolism, thrombophilia screening, or detection of coagulation factor deficiencies, respectively. Enzyme-linked immunosorbent assay (ELISA) and latex agglutination immunoassay technologies are currently most widely used, while Luminescent Oxygen Channeling Immuno - assay (LOCI®) and other chemiluminescencebased immunoassays are emerging technologies for the coagulation laboratory. However, not all immunoassay technologies employed are compatible with the workflow requirements of the coagulation laboratory, and, not all technologies are suitable for detection or quantification of every marker.

This review focuses on technical and performance aspects of those immunoassay technologies that are most widely used in the coagulation laboratory, and provides a description of markers that are typically tested by immunoassays.

Increased risk of early and medium-term revision after post-fracture total knee arthroplasty

Background and purpose - Total knee arthroplasty (TKA) due to posttraumatic fracture osteoarthritis (PTFA) may be associated with inferior prosthesis survival. This study is the first registry-based study solely addressing this issue. Both indications and predictors for revision were identified. Patients and methods - 52,518 primary TKAs performed between 1997 and 2013 were retrieved from the Danish Knee Arthroplasty Register (DKR). 1,421 TKAs were inserted due to PTFA and 51,097 due to primary osteoarthritis (OA). Short-term (< 1 year), medium-term (1-5 years), and long-term (> 5 years) implant survival were analyzed using Kaplan-Meier analysis and Cox regression after age stratification (< 50, 50-70, and >70 years). In addition, indications for revision and characteristics of TKA patients with subsequent revision were determined. Results - During the first 5 years, TKAs inserted due to PTFA had a higher risk of revision than OA (with adjusted hazard ratio ranging from 1.5 to 2.4 between age categories). After 5 years, no significant differences in the risk of revision were seen between the groups. Infection and aseptic loosening were the most common causes of revision in both groups, but TKA instability was a more frequent indication for revision in the PTFA group. In both groups, the revision rates were higher with younger age and extended duration of primary surgery. Interpretation - We found an increased risk of early and medium-term revision of TKAs inserted due to previous fractures in the distal femur and/or proximal tibia. Predictors of revision such as age <50 years and extended duration of primary surgery were identified, and revision due to instability occurred more frequently in TKAs performed due to previous fractures.

miRNA assays in the clinical laboratory: workflow, detection technologies and automation aspects

microRNAs (miRNAs) are short non-coding RNA molecules that regulate gene expression in eukaryotes. Their differential abundance is indicative or even causative for a variety of pathological processes including cancer or cardiovascular disorders. Due to their important biological function, miRNAs represent a promising class of novel biomarkers that may be used to diagnose life-threatening diseases, and to monitor disease progression. Further, they may guide treatment selection or dosage of drugs. miRNAs from blood or derived fractions are particularly interesting candidates for routine laboratory applications, as they can be measured in most clinical laboratories already today. This assures a good accessibility of respective tests. Albeit their great potential, miRNA-based diagnostic tests have not made their way yet into the clinical routine, and hence no standardized workflows have been established to measure miRNAs for patients' benefit. In this review we summarize the detection technologies and workflow options that exist to measure miRNAs, and we describe the advantages and disadvantages of each of these options. Moreover, we also provide a perspective on data analysis aspects that are vital for translation of raw data into actionable diagnostic test results.

Tourniquet induced ischemia and changes in metabolism during TKA: a randomized study using microdialysis

Background

Tourniquet use in total knee arthroplasty (TKA) surgery is applied to minimize blood loss thereby creating better overview of the surgical field. This induces ischemia in the skeletal muscle resulting in reperfusion injury. Our aim was to investigate the in vivo metabolic changes in the skeletal muscle during TKA surgery using microdialysis (MD).

Methods

Seventy patients were randomly allocated to tourniquet group (n = 35) or non-tourniquet group (n = 35). Prior to surgery, catheters were inserted in the operated leg and non-operated leg. Interstitial dialysate was collected before and after surgery and at 20 min intervals during a 5 h reperfusion period. Main variables were ischemic metabolites: glucose, pyruvate, lactate and glycerol and L/P ratio.

Results

Significant difference in all metabolites was detected between the two groups, caused by tourniquet application. Tourniquet induced ischemia resulted in decreased levels of glucose and pyruvate to 54 and 60 % respectively, compared to baseline. Simultaneously, accumulation of lactate to 116 % and glycerol to 190 % was observed. L/P ratio was elevated indicating ischemia.

In the non-tourniquet group the metabolite changes were less profound and normalized within 60 min.

Conclusions

Microdialysis revealed that performing TKA with tourniquet is associated with increased ischemia. This affects all metabolites but the changes are normalized after 5 h

MicroRNA In Vitro Diagnostics Using Immunoassay Analyzers

BACKGROUND

The implementation of new biomarkers into clinical practice is one of the most important areas in medical research. Besides their clinical impact, novel in vitro diagnostic markers promise to have a substantial effect on healthcare costs. Although numerous publications report the discovery of biomarkers, only a fraction of those markers are routinely used. One key challenge is a measurement system that is compatible with clinical workflows.

METHODS

We designed a new immunoassay for microRNA (miRNA) quantification. The assay combines streptavidin-linked microparticles, a biotinylated catcher oligonucleotide complementary to a single miRNA species, and finally, a monoclonal antibody to DNA/RNA heterohybrids labeled with acridinium ester. Importantly, our assay runs on standard immunoassay analyzers. After a technical validation of the assay, we evaluated the clinical performance on 4 Alzheimer disease miRNAs.

RESULTS

Our assay has an analytical specificity of 99.4% and is at the same time sensitive (concentrations in the range of 1 pmol/L miRNA can be reliably profiled). Because the novel approach did not require amplification steps, we obtained high reproducibility for up to 40 biological replicates. Importantly, our assay prototype exhibited a time to result of &lt;3 h. With human blood samples, the assay was able to measure 4 miRNAs that can detect Alzheimer disease with a diagnostic accuracy of 82% and showed a Pearson correlation &gt;0.994 with the gold standard qRT-PCR.

CONCLUSIONS

Our miRNA immunoassay allowed the measurement of miRNA signatures with sufficient analytical sensitivity and high specificity on commonly available laboratory equipment.

The dislocating hip replacement - revision with a dual mobility cup in 56 consecutive patients

INTRODUCTION

Recurrent dislocations of hip replacements are a difficult challenge. One treatment option for recurrent dislocations is the use of a dual mobility cup. The aim of this study was to retrospective investigate the effect of dual mobility cups as a treatment for recurrent dislocations in a consecutive series. Materials and.

METHODS

56 consecutive patients were revised in the period November 2000 to December 2010. The mean age at revision was 72 years (SD 11, range 37-92)) and median number of dislocations before revision surgery were 4 (IQR, 2-11). In all cases, revision was made with a Saturne dual mobility cup (Amplitude, Neyron, France). The mean follow-up period was 44 months (SD 30, range 0.1-119).

RESULTS

One patient (1.8%) experienced a re-dislocation. Three patients (5.3%) had to be revised. One due to disintegration between the femoral head and inner shell, one due to loosening of the acetabular component, and one due to infection. Harris Hip Score improved from a mean of 76 before index surgery to 87 within one year after index surgery.

CONCLUSION

This study advocates the use of a dual mobility cup for treatment of recurrent dislocations of THR. However, studies with a longer follow up are needed in order to evaluate implant survival.

Faster recovery without the use of a tourniquet in total knee arthroplasty

BACKGROUND AND PURPOSE

Tourniquet application is still a common practice in total knee arthroplasty (TKA) surgery despite being associated with several adverse effects. We evaluated the effects of tourniquet use on functional and clinical outcome and on knee range of motion (ROM).

PATIENTS AND METHODS

70 patients who underwent TKA were randomized into a tourniquet group (n = 35) and a non-tourniquet group (n = 35). All operations were performed by the same surgeon and follow-up was for 1 year. Primary outcomes were functional and clinical outcomes, as evaluated by KOOS and knee ROM. Secondary outcomes were intraoperative blood loss, surgical time and visibility, postoperative pain, analgesic consumption, and transfusion requirements.

RESULTS

Patients in the non-tourniquet group showed a better outcome in all KOOS subscores and better early knee ROM from surgery to week 8. No difference was detected at the 6- and 12-month follow-ups. Postoperative pain and analgesic consumption were less when a tourniquet was not used. Surgical time and visibility were similar between groups. Intraoperative blood loss was greater when not using a tourniquet, but no postoperative transfusions were required.

INTERPRETATION

This study shows that TKA without the use of a tourniquet results in faster recovery in terms of better functional outcome and improved knee ROM. Furthermore, reduced pain and analgesic use were registered and no intraoperative difficulties were encountered.

Comprehensive analysis of microRNA profiles in multiple sclerosis including next-generation sequencing

BACKGROUND

MicroRNAs (miRNAs) are short, noncoding RNAs with gene regulatory functions whose expression profiles may serve as disease biomarkers.

OBJECTIVE

The objective of this study was to perform a comprehensive analysis of miRNA expression profiles in blood of patients with a clinically isolated syndrome (CIS) or relapsing-remitting multiple sclerosis (RRMS) including next-generation sequencing (NGS).

METHODS

miRNA expression was analyzed in whole blood samples from treatment-naïve patients with CIS (n = 25) or RRMS (n = 25) and 50 healthy controls by NGS, microarray analysis, and quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

In patients with CIS/RRMS, NGS and microarray analysis identified 38 and eight significantly deregulated miRNAs, respectively. Three of these miRNAs were found to be significantly up- (hsa-miR-16-2-3p) or downregulated (hsa-miR-20a-5p, hsa-miR-7-1-3p) by both methods. Another five of the miRNAs significantly deregulated in the NGS screen showed the same direction of regulation in the microarray analysis. qRT-PCR confirmed the direction of regulation for all eight and was significant for three miRNAs.

CONCLUSIONS

This study identifies a set of miRNAs deregulated in CIS/RRMS and reconfirms the previously reported underexpression of hsa-miR-20a-5p in MS. hsa-miR-20a-5p and the other validated miRNAs may represent promising candidates for future evaluation as biomarkers for MS and could be of relevance in the pathophysiology of this disease.

Direct chromogenic substrate immuno-capture activity assay for testing of factor VII-activating protease

BACKGROUND

The Marburg I (MRI) single nucleotide polymorphism (SNP) of the factor VII-activating protease (FSAP) gene has been associated with thrombophilia and atherosclerotic disease. PCR is used to detect the SNP. Also, the specific FSAP activity to cleave single-chain urokinase-type plasminogen activator (scu-PA) serves as a surrogate for PCR testing. Development of further assays is indicated in order to increase testing opportunities for future studies.

METHODS

A direct chromogenic substrate immuno-capture activity assay for FSAP (FSAP dcs activity assay) was established. Performance characteristics of the FSAP dcs activity assay were compared to the FSAP scu-PA activity assay.

RESULTS

The FSAP dcs activity assay detects FSAP activity from 25% to 150% of the norm. Total CVs ranged from 6% to 10% for FSAP wild type samples and 9%-18% for MRI samples. Correlation between the FSAP dcs and scu-PA activity assays was low (R=0.7). The FSAP dcs activity determined the presence of the MRI FSAP alloenzyme with a diagnostic sensitivity and specificity of 100% [95% confidence interval (CI): 89.6%-100%] and 96.2% (95% CI: 93.2%-97.4%), respectively, whereas the specific FSAP dcs activity increased specificity to 99.0% (95% CI: 97.2%-99.6%).

CONCLUSIONS

The specific FSAP dcs activity represents a reliable method for the detection of the FSAP MRI alloenzyme. Due to the limited correlation between the FSAP dcs and scu-PA activity assays, these different measurands may exhibit different utility in research and clinical applications. Thus, the FSAP dcs activity assay can represent a valuable complement or alternative for FSAP testing in future studies.

Fully automated immunoassay for quantitative determination of FXIII

Coagulation factor XIII (FXIII) is essential for clot stabilization. Deficiency of FXIII is associated with a risk of bleeding and impaired wound healing. Substitution therapy with FXIII remedies for patients with low plasma levels of FXIII requires diagnostic quantification of the factor before and during therapy. Here, we describe a prototype of a preliminary research immunoassay for quantification of FXIII antigen on automated coagulation instruments. The prototype assay is based on a monoclonal antibody (mAb) directed against FXIII A chain, whereas the mAbs are coupled to latex particles. FXIII in a plasma specimen causes agglutination of the latex particles, which can be quantified turbidimetrically. Performance data of the assay prototype processed on BCS® XP and Sysmex® CA-1500 instruments demonstrate a good correlation to the Berichrom® factor XIII activity assay1 from Siemens Healthcare Diagnostics (r = 0.94). Results: Comparability of instruments was excellent (r = 0.98). Coefficients of variation of total imprecision measurements ranged from 2.2 to 3.4%. Linearity was excellent over the range tested (12–121% FXIII). Analytical sensitivity was 0.51% FXIII on BCS XP and 0.44% FXIII on Sysmex CA-1500, respectively. No interference (> 10% bias) was observed with haemoglobin (up to 400 mg/dl), cholesterol (up to 300 mg/dl), bilirubin (up to 60 mg/dl) or triglycerides (up to 3000 mg/dl). Conclusion: The preliminary research assay prototype has the potential for excellent analytical sensitivity, precision, and dynamic range suitable to measure reliably FXIII antigen levels in human plasma.

Immunoassays for diagnosis of coagulation disorders

Immunoassays play a pivotal role in the clinical laboratory. In the coagulation section of the laboratory, they are used as an aid for diagnosis of deep vein thrombosis or pulmonary embolism, thrombophilia screening, or detection of coagulation factor deficiencies, respectively. Enzyme-linked immunosorbent assay (ELISA) and latex agglutination immunoassay technologies are currently most widely used, while Luminescent Oxygen Channeling Immunoassay (LOCI®) and other chemiluminescence-based immunoassays are emerging technologies for the coagulation laboratory. However, not all immunoassay technologies employed are compatible with the workflow requirements of the coagulation laboratory, and, not all technologies are suitable for detection or quantification of every marker. This review focuses on technical and performance aspects of those immunoassay technologies that are most widely used in the coagulation laboratory, and provides a description of markers that are typically tested by immunoassays.

Qualitative detection of the Marburg I alloenzyme of factor VII-activating protease by an immunoassay and its comparison to PCR testing

BACKGROUND

The Marburg I (MRI) single nucleotide polymorphism (SNP) of the factor VII-activating protease (FSAP) gene has been associated with thrombophilia, thromboembolism, atherosclerosis, and the incidence and progression of carotid stenosis. At present, MRI SNP testing is mainly performed using costly nucleic acid analysis. The ratio between FSAP activity and antigen concentrations in citrated plasma has been used to assess the FSAP genotype.

METHODS

This article describes the development of a prototype ELISA for the detection of the MRI FSAP alloenzyme, and its correlation to FSAP genotypes to assess whether a positive MRI FSAP ELISA result may be used as a surrogate marker for the presence of the MRI SNP.

RESULTS

ELISA results were correlated with FSAP genotypes from 523 blood donors measured using PCR. Diagnostic sensitivity and specificity of the assay for determination of the genotype were 100% (95% confidence interval [CI]: 93.36-100) and 99.79% (95% CI: 98.80-99.96), respectively. Maximum run-to-run, within-run, and total coefficients of variation were 7.8%, 7.9%, and 9.9%, respectively. No cross-reactivities with homologues of the MRI FSAP alloenzyme were observed. Test performance was not affected by typical interfering compounds.

CONCLUSIONS

The data demonstrate that an immunoassay applying antibodies specific to the MRI FSAP alloenzyme can provide sufficiently accurate detection of the MRI SNP. This will significantly simplify MRI FSAP testing, particularly in large cohorts.

Quantification of coagulation factor XIII activity by a thio-NADH based assay using factor XIII immuno-depleted plasma as a diluent for calibration

BACKGROUND

Accurate determination of factor XIII (FXIII) activity is crucial for replacement therapy. FXIII activity is typically determined using a coupled enzymatic reaction that measures nicotinamide adenine dinucleotide hydride (NADH) consumption at 340 nm.

METHODS

Here, we describe the development of a prototype for a novel FXIII activity assay for detection at 405 nm by replacing NADH with thio-NADH, and the application of FXIII immuno-depleted plasma as a diluent for calibration.

RESULTS

Performance data show up to two-fold lower susceptibility of the prototype assay to interferences from hemolyzed, icteric, and lipemic samples when compared to a NADH assay format. In addition, the use of FXIII immuno-depleted plasma as diluent for calibration improved recovery almost two-fold in the lower measurement range. The novel prototype assay correlates well with a conventional assay (r=0.98, y=0.99·x+2.17% FXIII, n=173).

CONCLUSIONS

The described prototype assay has the potential to (a) increase trueness of measurement of low levels of FXIII, (b) improve robustness due to reduction from interferences, and (c) can be used on a broad range of coagulation instruments due to its detection at 405 nm.

Constitutive activation of the Ras-Raf signaling pathway in metastatic melanoma is associated with poor prognosis

Background

Genes of the Raf family encode kinases that are regulated by Ras and mediate cellular responses to growth signals. Recently, it was shown that activating mutations of BRaf are found with high frequency in human melanomas. The Ras family member most often mutated in melanoma is NRas.

Methods

The constitutive activation of the Ras/Raf signaling pathway suggests an impact on the clinical course of the tumor. To address this notion, we analyzed tumor DNA from 114 primary cutaneous melanomas and of 86 metastatic lesions obtained from 174 patients for mutations in BRaf (exons 15 and 11) and NRas (exons 1 and 2) by direct sequencing of PCR products and correlated these results with the clinical course.

Results

In 57.5% of the tumors either BRaf or NRas were mutated with a higher incidence in metastatic (66.3%) than in primary lesions (50.9%). Although the majority of BRaf mutations affected codon 599, almost 15% of mutations at this position were different from the well-described exchange from valine to glutamic acid. These mutations (V599R and V599K) also displayed increased kinase and transforming activity. Surprisingly, the additional BRaf variants D593V, G465R and G465E showed a complete loss of activity in the in vitro kinase assay; however, cells overexpressing these mutants displayed increased Erk phosphorylation. The correlation of mutational status and clinical course revealed that the presence of BRaf/NRas mutations in primary tumors did not negatively impact progression free or overall survival. In contrast, however, for metastatic lesions the presence of BRAF/NRAS mutations was associated with a significantly poorer prognosis, i.e. a shortened survival.

Conclusion

We demonstrate a high – albeit lower than initially anticipated – frequency of activating BRaf mutations in melanoma in the largest series of directly analyzed tumors reported to date. Notably, the clinical course of patients harboring activating BRaf mutations in metastatic melanoma was significantly affected by the presence of a constitutive BRaf activation in these.

Cooperative interaction of hypoxia-inducible factor-2alpha (HIF-2alpha ) and Ets-1 in the transcriptional activation of vascular endothelial growth factor receptor-2 (Flk-1)

Interactions between Ets family members and a variety of other transcription factors serve important functions during development and differentiation processes, e.g. in the hematopoietic system. Here we show that the endothelial basic helix-loop-helix PAS domain transcription factor, hypoxia-inducible factor-2alpha (HIF-2alpha) (but not its close relative HIF-1alpha), cooperates with Ets-1 in activating transcription of the vascular endothelial growth factor receptor-2 (VEGF-2) gene (Flk-1). The receptor tyrosine kinase Flk-1 is indispensable for angiogenesis, and its expression is closely regulated during development. Consistent with the hypothesis that HIF-2alpha controls the expression of Flk-1 in vivo, we show here that HIF-2alpha and Flk-1 are co-regulated in postnatal mouse brain capillaries. A tandem HIF-2alpha/Ets binding site was identified within the Flk-1 promoter that acted as a strong enhancer element. Based on the analysis of transgenic mouse embryos, these motifs are essential for endothelial cell-specific reporter gene expression. A single HIF-2alpha/Ets element conferred strong cooperative induction by HIF-2alpha and Ets-1 when fused to a heterologous promoter and was most active in endothelial cells. The physical interaction of HIF-2alpha with Ets-1 was demonstrated and localized to the HIF-2alpha carboxyl terminus and the autoinhibitory exon VII domain of Ets-1, respectively. The deletion of the DNA binding and carboxyl-terminal transactivation domains of HIF-2alpha, respectively, created dominant negative mutants that suppressed transactivation by the wild type protein and failed to synergize with Ets-1. These results suggest that the interaction between HIF-2alpha and endothelial Ets factors is required for the full transcriptional activation of Flk-1 in endothelial cells and may therefore represent a future target for the manipulation of angiogenesis.

Rapid parallel mutation scanning of gene fragments using a microelectronic protein-DNA chip format

We have developed a method for the de novo discovery of genetic variations, including single nucleotide polymorphisms and mutations, on microelectronic chip devices. The method combines the features of electronically controlled DNA hybridisation on open-format microarrays, with mutation detection by a fluorescence-labelled mismatch- binding protein. Electronic addressing of DNA strands to distinct test sites of the chip allows parallel analysis of several individuals, as demonstrated for mutations in different exons of the p53 gene. This microelectronic chip-based mutation discovery assay may substitute for time-consuming sequencing studies and will complement existing technologies in genomic research.

Hypoxia-inducible factor-1alpha mRNA contains an internal ribosome entry site that allows efficient translation during normoxia and hypoxia

HIF-1alpha is the regulated subunit of the HIF-1 transcription factor, which induces transcription of a number of genes involved in the cellular response to hypoxia. The HIF-1alpha protein is rapidly degraded in cells supplied with adequate oxygen but is stabilized in hypoxic cells. Using polysome profile analysis, we found that translation of HIF-1alpha mRNA in NIH3T3 cells is spared the general reduction in translation rate that occurs during hypoxia. To assess whether the 5'UTR of the HIF-1alpha mRNA contains an internal ribosome entry site (IRES), we constructed a dicistronic reporter with the HIF-1alpha 5'UTR inserted between two reporter coding regions. We found that the HIF-1alpha 5'UTR promoted translation of the downstream reporter, indicating the presence of an IRES. The IRES had activity comparable to that of the well-characterized c-myc IRES. IRES activity was not affected by hypoxic conditions that caused a reduction in cap-dependent translation, and IRES activity was less affected by serum-starvation than was cap-dependent translation. These data indicate that the presence of an IRES in the HIF-1alpha 5'UTR allows translation to be maintained under conditions that are inhibitory to cap-dependent translation.

Role of SCL/Tal-1, GATA, and ets transcription factor binding sites for the regulation of flk-1 expression during murine vascular development

The receptor tyrosine kinase Flk-1 is essential for embryonic blood vessel development and for tumor angiogenesis. To identify upstream transcriptional regulators of Flk-1, the gene regulatory elements that mediate endothelium-specific expression in mouse embryos were characterized. By mutational analysis, binding sites for SCL/Tal-1, GATA, and Ets transcription factors located in the Flk-1 enhancer were identified as critical elements for the endothelium-specific Flk-1 gene expression in transgenic mice. c-Ets1, a transcription factor that is coexpressed with Flk-1 during embryonic development and tumor angiogenesis, activated the Flk-1 promoter via 2 binding sites. One of these sites was required for Flk-1 promoter function in the embryonic vasculature. These results provide the first evidence that SCL/Tal-1, GATA, and Ets transcription factors act upstream of Flk-1 in a combinatorial fashion to determine embryonic blood vessel formation and are key regulators not only of the hematopoietic program, but also of vascular development.

Tumor endothelium-specific transgene expression directed by vascular endothelial growth factor receptor-2 (Flk-1) promoter/enhancer sequences

The receptor tyrosine kinase Flk-1 plays a pivotal role in the development of the vascular system and in the vascularization of a wide variety of tumors. We have investigated the activity of cis-acting sequences of the murine Flk-1 gene in the tumor endothelium of experimental tumor models in vivo. B16 melanoma, BFS-1 fibrosarcoma, and polyoma middle T-induced mammary adenocarcinoma were grown in transgenic mice that express the LacZ reporter gene under the control of a 939-bp Flk-1 promoter fragment and an enhancer element located in a 2.3-kb fragment of the first intron. In all experimental tumor models examined, strong endothelium-specific reporter gene expression was observed while being absent from most blood vessels in normal adult tissue. The expression patterns of the LacZ reporter gene correlate well between established tumors grown in Flk1-LacZ transgenic mice and tumors grown in Flk-1+/LacZ knock-in mice that express the LacZ reporter gene from the endogenous Flk-1 locus. The endothelium-specific activity of the Flk-1 promoter/enhancer sequences in three different experimental tumor models demonstrates that the regulatory sequences that mediate the up-regulation of Flk-1 in the tumor endothelium are contained in the Flk-1 promoter/enhancer sequences used, and that these elements function relatively independently of the tumor type. The Flk-1 promoter/enhancer sequences should allow the analysis of the signaling pathways that lead to the up-regulation of Flk-1 in the tumor endothelium and to specifically target therapeutic genes to the endothelium of tumors for antiangiogenic tumor therapy.

mRNA cloning and expression studies of the quail homologue of HIF-2alpha

Hypoxia inducible factors (HIF) are candidate transcriptional regulators of vascular development. Unlike HIF-1alpha - the founding member of the HIF family - which is expressed more or less ubiquitously, HIF-2alpha (also called HRF, HLF and EPAS1) is highly expressed by vascular endothelial cells and was shown to activate the transcription of endothelial cell-specific receptor tyrosine kinases (tie-2 and flk-1/VEGF receptor 2) and of vascular endothelial growth factor (VEGF). Therefore HIF-2alpha is a candidate dual regulator of vascular development. Here we describe the quail homologue of HIF-2alpha. Sequence analysis reveals that HIF-2alpha is highly conserved between birds and mammals. Like the murine HIF-2alpha, the quail molecule is highly expressed by endothelial cells but also detectable in certain epithelial cells such as in the endoderm.

Identification of vascular endothelial growth factor (VEGF) receptor-2 (Flk-1) promoter/enhancer sequences sufficient for angioblast and endothelial cell-specific transcription in transgenic mice

The vascular endothelial growth factor (VEGF) receptor-2 (Flk-1) is the first endothelial receptor tyrosine kinase to be expressed in angioblast precursors, and its function is essential for the differentiation of endothelial cells and hematopoietic precursors. We have identified cis-acting regulatory elements of the murine Flk-1 gene that mediate endothelium-specific expression of a LacZ reporter gene in transgenic mice. Sequences within the 5'-flanking region of the Flk-1 gene, in combination with sequences located in the first intron, specifically targeted transgene expression to angioblasts and endothelial cells of transgenic mice. The intronic regulatory sequences functioned as an autonomous endothelium-specific enhancer. Sequences of the 5'-flanking region contributed to a strong, uniform, and reproducible transgene expression and were stimulated by the transcription factor HIF-2alpha. The Flk-1 gene regulatory elements described in this study should allow the elucidation of the molecular mechanisms involved in endothelial cell differentiation and angiogenesis.

HRF, a putative basic helix-loop-helix-PAS-domain transcription factor is closely related to hypoxia-inducible factor-1 alpha and developmentally expressed in blood vessels

Transcription factors of the bHLH-PAS protein family are important regulators of developmental processes such as neurogenesis and tracheal development in invertebrates. Recently a bHLH-PAS protein, named trachealess (trl) was identified as a master regulator of tracheogenesis. Hypoxia-inducible factor, HIF-1 alpha, is a vertebrate relative of trl which is likely to be involved in growth of blood vessels by the induction of vascular endothelial growth factor (VEGF) in response to hypoxia. In the present study we describe mRNA cloning and mRNA expression pattern of mouse HIF-related factor (HRF), a novel close relative of HIF-1 alpha which is expressed most prominently in brain capillary endothelial cells and other blood vessels as well as in bronchial epithelium in the embryo and the adult. In addition, smooth muscle cells of the uterus, neurons, brown adipose tissue and various epithelial tissues express HRF mRNA as well. High expression levels of HRF mRNA in embryonic choroid plexus and kidney glomeruli, places where VEGF is highly expressed, suggest a role of this factor in VEGF gene activation similar to that of HIF-1 alpha. Given the similarity between morphogenesis of the tracheal system and the vertebrate vascular system, the expression pattern of HRF in the vasculature and the bronchial tree raises the possibility that this family of transcription factors may be involved in tubulogenesis.