Neutrophil CD64 expression in the diagnosis of local musculoskeletal infection and the impact of antibiotics

Serum CD64 as a Marker for Chronic Periprosthetic Joint Infection

Background

Serum cluster of differentiation 64 (CD64) has emerged as a diagnostic test for musculoskeletal infections. The purpose of this study was to evaluate the utility of serum CD64 in diagnosing periprosthetic joint infections (PJIs) compared to conventional markers like white blood count (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and interleukin-6 (IL-6).

Methods

A prospective case-control study on patients undergoing revision hip or knee arthroplasty surgery >6 weeks after their index surgery was performed at a single institution. Whole blood samples were drawn within 24 hours prior to revision surgery for white blood count, ESR, CRP, IL-6, and CD64. Intraoperative cultures were obtained during the revision, and PJI was defined using the major criteria from the 2018 Musculoskeletal Infection Society criteria. Two-sample Wilcoxon rank-sum test and Fisher's exact test were used to determine if there were significant differences in serum laboratory values between patients with and without infection. The sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy of each test were calculated.

Results

With an average age of 67 years, 39 patients with 15 revision THAs and 24 TKAs, were included. 19 patients (48.7%) were determined to have PJI. Patients with PJI had significantly higher CD64 (P = .036), CRP (P = .016), and ESR (P = .045). CD64 had the highest specificity (100%) and PPV (100%), moderate accuracy (69.2%), but low sensitivity (37.0%) and negative predictive value (62.5%).

Conclusions

Given the high specificity, PPV, and accuracy, CD64 may be an excellent confirmatory test to help diagnose PJI.

Analysis of Risk Factors and Association of Cluster of Differentiation (CD) Markers With Conventional Markers in Delayed Fracture Related Infection for Closed Fracture

Background: Fracture-related infections (FRI) remain a difficult consequence for orthopedic trauma patients, their relatives, the treating physicians, and the healthcare systems. Delayed fracture-related infection is an important step in the infection process that can be controlled by diagnosing and preventing it from moving to the next level. Neutrophils CD64 and CD66b were identified as sensitive indicators in the event of infection. Normal sequential changes, on the other hand, occur after surgery and are extremely high. They are back to normal on the 10^th day after the operation. The aim of this study was, therefore, to examine the risk factors associated with fracture-related infection by comparing cluster of differentiation (CD) indicators with conventional markers and comparing them with gold standards culture reports. As a result, it could be an early sign of a closed fracture infection.

Material & Methods: Between February 2020 and March 2021, 510 patients from the Department of Orthopedics at King George Medical University in Lucknow agreed to participate in the study. The study included patients who had a closed fracture and had undergone elective or emergency surgery. Blood was withdrawn before the surgery (baseline) on day one and again on the third, seventh, and 10^th day after the operation to measure the quantitative measurements of the biomarkers (total leucocyte count [TLC], erythrocyte sedimentation rate [ESR], C reactive protein [CRP], CD64, and CD66b) in all follow-up examinations. Patients were monitored for delayed signs of the infection for 2 to 10 weeks. The biomarkers were evaluated and linked to the culture reports.

Results: Of the 510 patients included, 272 were men (53.3%) and 238 women (46.7%), the mean age was 40 (20-78), the mean age for fracture related infection with positive culture (FRI POS) was 48.0 (SD: 19.47), for fracture related infection with negative culture (FRI NEG) was 46.20 (SD: 17.18), and for patient with no signs of infections (NON-FRI) was 45.13 (SD: 17.62) (p <0.001), the mean duration of the fracture to admission (in hours) was 4.90 (SD: 1.92), 4.91 (SD: 2.65), and 5.14 (SD: 2.66) (p <0.001), respectively. The mean duration of admission to surgery (in hours) was 31.54 (SD: 85.14), 43.14 (SD: 105.64), and 61.84 (134.14), respectively (p <0.001). The mean duration of surgery was 4.63 (SD: 1.85), 5.14 (SD: 2.16), and 5.05 (SD: 2.16) (p <0.001). The risk factors such as bone type (p = 0.04) and addiction (p = 0.01) were identified as statistically significant. There was no correlation between the CD66b markers on the third, seventh, and 10^th days. CD64 was significantly correlated with ESR, TLC, and CRP on the 10^th day in the FRI-positive group (r = 0.638; p = 0.03) (r = 0.744; p = 0.009) (r = 0.817; p = 0.002).

Conclusion: The risk factors for infection in fracture patients are significantly influenced by the type of bone and addiction the patient is using. Elevated CD64 levels could be used as a diagnostic marker for infection early on the 10^th day after surgery before the appearance of clinical signs.

A Clinical Pilot Study to Evaluate CD64 Expression on Blood Monocytes as an Indicator of Periprosthetic Joint Infection

BACKGROUND

The preoperative diagnosis of periprosthetic joint infection (PJI) depends on a series of blood biomarkers. Previous studies have shown that CD64 expression on blood neutrophils and monocytes has a good diagnostic efficacy for diagnosing systemic and local infections. The purpose of the present study was to investigate the role of blood CD64 in the diagnosis of PJI.

METHODS

On the basis of estimations made before the study was performed, 62 patients were recruited for joint revision surgery following the failure of primary hip or knee replacement. Venous blood was obtained within 24 hours after patient admission, and flow cytometry was performed to evaluate the CD64 expression of 3 groups of white blood cells (WBCs). CD64 expression was measured as CD64 mean fluorescence intensity (CD64MFI). The neutrophil CD64 index (nCD64 index; neutrophil CD64MFI [nCD64MFI]/lymphocyte CD64MFI [lCD64MFI]) and monocyte CD64 index (mCD64 index; monocyte CD64MFI [mCD64MFI]/lCD64MFI) were then calculated. The C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) at admission, synovial fluid indicators, leukocyte esterase test results, intraoperative histological results, and tissue or synovial fluid culture results were recorded. According to the modified Musculoskeletal Infection Society (MSIS) criteria, patients were divided into the PJI group and the non-PJI group. These blood indicators were then analyzed for the diagnosis of PJI.

RESULTS

The PJI group included 18 patients, and the non-PJI group included 44 patients. The diagnostic value of the area under the receiver operating characteristic curve (AUC) was low for lCD64MFI, the nCD64 index, and the mCD64 index. The diagnostic value for nCD64MFI was moderate, with an AUC of 0.735 (95% confidence interval [CI], 0.595 to 0.874; p = 0.004). The diagnostic value for mCD64MFI was high, with an AUC of 0.898 (95% CI, 0.821 to 0.975; p < 0.001). The cutoff value for mCD64MFI was 28,968, with a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 1, 0.75, 0.62, and 1, respectively. This result was confirmed by internal validation with a different antibody.

CONCLUSIONS

Flow cytometry can be used for patient screening before revision surgery, and blood mCD64MFI is a promising indicator for PJI.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Differential Accumulation and Activation of Monocyte and Dendritic Cell Subsets in Inflamed Synovial Fluid Discriminates Between Juvenile Idiopathic Arthritis and Septic Arthritis

Despite their distinct etiology, several lines of evidence suggest that innate immunity plays a pivotal role in both juvenile idiopathic arthritis (JIA) and septic arthritis (SA) pathophysiology. Indeed, monocytes and dendritic cells (DC) are involved in the first line of defense against pathogens and play a critical role in initiating and orchestrating the immune response. The aim of this study was to compare the number and phenotype of monocytes and DCs in peripheral blood (PB) and synovial fluid (SF) from patients with JIA and SA to identify specific cell subsets and activation markers associated with pathophysiological mechanisms and that could be used as biomarkers to discriminate both diseases. The proportion of intermediate and non-classical monocytes in the SF and PB, respectively, were significantly higher in JIA than in SA patients. In contrast the proportion of classical monocytes and their absolute numbers were higher in the SF from SA compared with JIA patients. Higher expression of CD64 on non-classical monocyte was observed in PB from SA compared with JIA patients. In SF, higher expression of CD64 on classical and intermediate monocyte as well as higher CD163 expression on intermediate monocytes was observed in SA compared with JIA patients. Moreover, whereas the number of conventional (cDC), plasmacytoid (pDC) and inflammatory (infDC) DCs was comparable between groups in PB, the number of CD141⁺ cDCs and CD123⁺ pDCs in the SF was significantly higher in JIA than in SA patients. CD14⁺ infDCs represented the major DC subset in the SF of both groups with potent activation assessed by high expression of HLA-DR and CD86 and significant up-regulation of HLA-DR expression in SA compared with JIA patients. Finally, higher activation of SF DC subsets was monitored in SA compared with JIA with significant up-regulation of CD86 and PDL2 expression on several DC subsets. Our results show the differential accumulation and activation of innate immune cells between septic and inflammatory arthritis. They strongly indicate that the relative high numbers of CD141⁺ cDC and CD123⁺ pDCs in SF are specific for JIA while the over-activation of DC and monocyte subsets is specific for SA.

Utility of CD64 on Neutrophils in Orthopedic Infection

Background

Musculoskeletal infections are often seen in the daily practice of orthopedics. Several markers [white blood cell (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), procalcitonin (PCT)] have been used for diagnosing these infections. However, these markers may be elevated due to surgery or trauma, and may not be infection-related. These markers also show drug-dependent dynamics during infection that differ from its usual dynamics. Such situations make diagnosis of infections difficult, and Cluster of Differentiation 64 (CD64) has been brought to attention. This study aimed to clarify the utility of CD64 on neutrophils by comparing it with conventional infection markers (CRP, PCT) in musculoskeletal infection.

Methods

Forty-four patients who were suspected of having musculoskeletal infection between May 2010 and November 2013 in our hospital were enrolled in this study. Patients were divided into subgroups according to their culture results, antibiotics administration, measurement timing, and if they were immunocompromised. The measurements of the infection markers were compared between each group. In addition, the positive rates of each infection marker were compared between groups.

Results

There was no difference in the infection marker measurements between several groups. There was no statistically significant difference between groups for the positive rates of CD64, CRP, and PCT.

Conclusion

We evaluated the utility of CD64 on neutrophils in musculoskeletal infection. CD64 showed the utility that was equivalent to conventional infection markers in diagnoses of various musculoskeletal infections.

A point-of-care microfluidic biochip for quantification of CD64 expression from whole blood for sepsis stratification

Sepsis, a potentially life-threatening complication of an infection, has the highest burden of death and medical expenses in hospitals worldwide. Leukocyte count and CD64 expression on neutrophils (nCD64) are known to correlate strongly with improved sensitivity and specificity of sepsis diagnosis at its onset. A major challenge is the lack of a rapid and accurate point-of-care (PoC) device that can perform these measurements from a minute blood sample. Here, we report a PoC microfluidic biochip to enumerate leukocytes and quantify nCD64 levels from 10 μl of whole blood without any manual processing. Biochip measurements have shown excellent correlation with the results from flow cytometer. In clinical studies, we have used PoC biochip to monitor leukocyte counts and nCD64 levels from patients’ blood at different times of their stay in the hospital. Furthermore, we have shown the biochip’s utility for improved sepsis diagnosis by combining these measurements with electronic medical record (EMR).

Sepsis is a potentially life–threatening complication of infection and diagnosis depends on rapid assessment of leukocyte count and CD64 expression. Here the authors present a microfluidic chip that can quantify these parameters from minimal amounts of whole blood with no manual processing.

The usefulness of neutrophil CD64 expression for diagnosing infection after orthopaedic surgery in dialysis patients

BACKGROUND

Dialysis patients undergoing orthopaedic surgery are at high risk for postoperative infection. Diagnosis of postoperative infection is difficult in dialysis patients due to presentation of signs and symptoms similar to infection, such as fever and elevated inflammatory marker levels. Neutrophil CD64 expression (CD64), a marker of infection, is upregulated by microbial wall components and several cytokines (interferon-γ and tumor necrosis factor-α). The purpose of this study is to evaluate the usefulness of CD64 for diagnosing postoperative infection in dialysis patients post orthopaedic surgery.

PATIENTS AND METHODS

Between 2013 and 2014, we prospectively studied 36 dialysis patients (18 men, 18 women; mean age 65.9 years; 49 to 83) who underwent orthopaedic surgery. Dialysis patients were classified into three groups according to their postoperative course as follows; non-infected patients, infection suspected patients, and infected patients. Inflammatory markers such as white blood cell count (WBC), C-reactive protein (CRP) and CD64 were measured before operation and one week after surgery. Using the receiver-operating characteristic (ROC) curve and Akaike's Information Criterion (AIC), the cutoff value of CD64 and CRP was calculated leading to a determination of which inflammatory marker is best accurate for detecting postoperative infection.

RESULTS

We found that postoperative CD64 and CRP levels presented a statistically significant difference between infected patients and non-infected patients (p < 0.05). Furthermore, comparison of the ROC curve and AIC value between postoperative CD64 and CRP levels exhibited that CD64 was more accurate infectious marker than CRP.

CONCLUSION

CD64 is a useful marker for detecting postoperative infection after orthopaedic surgery in dialysis patients.

Neutrophil CD64 as a Marker of Bacterial Infection in Acute Exacerbations of Chronic Obstructive Pulmonary Disease

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are responsible for most mortality in patients with chronic obstructive pulmonary disease (COPD) and are caused mainly by bacterial infection. We analyzed and compared neutrophil CD64 expression (using the ratio of CD64 level in neutrophils to that in lymphocytes as an index), serum C-reactive protein (CRP), procalcitonin (PCT) levels, white blood cell (WBC) count, and neutrophil percentage among healthy subjects and patients with stable COPD or AECOPD. Compared with patients with COPD and healthy subjects, patients with AECOPD demonstrated significantly increased CD64 index, CRP, PCT, WBC count, and neutrophil percentage. Interestingly, CD64 index and PCT were both significantly higher in patients with AECOPD with positive bacterial sputum culture than those with negative culture. Furthermore, CD64 index and PCT were positively correlated in AECOPD, and there was also correlation between CD64 index and CRP, WBC, and neutrophil percentage. These data suggest that CD64 index is a relevant marker of bacterial infection in AECOPD. We divided patients with AECOPD into CD64-guided group and conventional treatment group. In CD64-guided group, clinicians prescribed antibiotics based on CD64 index; while in the conventional treatment group, clinicians relied on experience and clinical symptoms to determine the necessity for antibiotics. We found that the efficacy of antibiotic treatment in CD64-guided group was significantly improved compared with the conventional treatment group, including reduction of hospital stays and cost and shortened antibiotic treatment duration. Thus, the CD64 index has important diagnostic and therapeutic implications for antibiotic treatment of patients with AECOPD.

Monocyte HLA-DR expression and neutrophil CD64 expression as biomarkers of infection in critically ill neonates and infants

BACKGROUND

Reduced monocyte HLA-DR expression and increased neutrophil CD64 expression have been proposed as biomarkers of infection.

METHODS

From 2009-2011, blood samples from neonatal intensive care unit (NICU) and pediatric intensive care unit (ICU) patients <1 y of age were collected at enrollment and during subsequent evaluation for suspected infection, if it occurred. Samples were analyzed for monocyte HLA-DR and neutrophil CD64 expression levels by flow cytometry.

RESULTS

Forty-seven infants had study samples collected at enrollment; 26 infants had study samples collected at the time of a suspected infection. At enrollment, there was an inverse relationship between neutrophil CD64 expression and age (P ≤ 0.047). At the time of suspected infection, infants with an infection demonstrated a lower percentage of HLA-DR+ monocytes (P = 0.02, area under the curve (AUC) 0.78), higher percentage of CD64+ neutrophils (P = 0.009, AUC 0.81), and higher neutrophil CD64 expression levels (P = 0.04, AUC 0.75).

CONCLUSION

Monocyte HLA-DR and neutrophil CD64 expression in critically ill infants are related to age and infection.

Kinetics of leukocyte CD11b and CD64 expression in severe sepsis and non-infectious critical care patients

BACKGROUND

Leukocyte surface molecules may improve sepsis diagnostics. Our aim was to study whether monocyte and neutrophil CD11b and CD64 expression differs between patients with severe sepsis (including septic shock) and intensive care unit (ICU) controls, and also to investigate the expression kinetics in patient groups.

METHODS

Monocyte and neutrophil CD11b and CD64 expression was analyzed in 27 patients with severe sepsis, 7 off-pump coronary artery bypass (OPCAB) patients, and 8 ICU patients without systemic inflammation in the beginning of the treatment using quantitative flow cytometry. Blood samples were collected within 48 h of the beginning of severe sepsis, at admission to the ICU for non-systemic inflammatory response syndrome patients, and on the day of surgery before the skin incision for OPCAB patients, and on 2 consecutive days for all patients. Ten healthy individuals served as controls.

RESULTS

Monocyte and neutrophil CD11b and neutrophil CD64 expression was higher in severe sepsis patients compared with the other groups (P < 0.05). In severe sepsis, the expression decreased over time (P < 0.05). In OPCAB patients, the monocyte and neutrophil CD64 expression increased after surgery (P < 0.05). Neutrophil CD64 expression had the highest and statistically significant area under curves (AUC) values for identification of severe sepsis during 3 consecutive days, the highest AUC being 0.990 on D0.

CONCLUSION

Neutrophil CD64 as well as neutrophil and monocyte CD11b expressions were highest in severe sepsis compared with non-infectious conditions, and thus analyses of their expression may be promising approach for sepsis diagnosis in ICU population.

The assessment of neutrophil CD64 count as an early warning marker of joint replacement infection

120,000 hip and knee replacements are performed each year in the UK and more than 1 % of these require revision surgery due to infection. Current diagnostic tests used to diagnose infection of joint replacements, including the current gold standard C-reactive protein, which offers poor specificity when diagnosing infection in the post-operative period. In the post-operative period these tests are unable to differentiate between physiological inflammation and infection of the replacement. Early treatment through antibiotic and washout therapy is essential to eradicate infection, saving the patient and the NHS the stress of revision surgery, which offers a much poorer prognosis than the original operative procedure. Thus, a superior marker is required and CD64 has been proposed to fulfil the necessary requirements of an effective marker. Data from several studies utilising a flow cytometer support the view that CD64 is firstly, a good marker of systemic infection and secondly, when studied in conjunction with musculoskeletal infections alone, is a sensitive and specific marker of this type of infection. However, meta-analysis of studies in this field concludes that more highly powered studies are needed before definite conclusions can be drawn. Despite this, the studies do portray a strong case for CD64 being the future of diagnosis of post-operative infection.

CD64 as a potential biomarker in septic arthritis

Background

Traditional inflammatory markers are generally unhelpful in discerning septic arthritis from inflammatory joint disease due to their lack of specificity. We wished to explore the discriminatory power of the novel inflammatory marker, Fc-gamma-receptor type 1, CD64, in patients presenting with acute arthritis.

Methods

Patients were recruited prospectively in the time period June 2009 to December 2011. Thirty-six patients presenting with an acute flare of chronic rheumatic arthritis, 31 with crystal-induced arthritis and 23 with septic arthritis were included. Traditional inflammatory markers, CD64 and procalcitonin (PCT) were measured and their diagnostic abilities were compared.

Results

CD64 and PCT both demonstrated a specificity of 98%, but poor sensitivities of 59% and 52%, respectively. White blood cell count (WBC), and erythrocyte sedimentation rate (ESR) did not have significant discriminatory power, while C-reactive protein (CRP) proved to have the best diagnostic accuracy as measured by area under the ROC curve (AUC 0.92, 95% confidence-interval 0.87-0.98). Subgroup analysis excluding patients with septic arthritis without concurrent bacteremia, and likewise exclusion of the patients with septic arthritis caused by coagulase negative staphylococci, both improved the diagnostic accuracy of CD64 and PCT, but not of WBC and CRP.

Conclusions

CD64 and PCT are highly specific for infectious disease, but they predominantly measure bacteremia. Their use in hospital practice has yet to be defined, and especially so in localized infections.

Normal sequential changes in neutrophil CD64 expression after total joint arthroplasty

BACKGROUND

Neutrophil CD64 has been reported to be a sensitive and specific infection marker. Its measurement is thus considered to be useful in early diagnosis of post-operative periprosthetic infection. However, even its normal sequential changes after non-infectious total joint arthroplasty have remained ambiguous. Accordingly, we analyzed 2-week sequential neutrophil CD64 expression changes after total joint arthroplasty in order to clarify its normal postoperative kinetics.

PATIENTS AND METHOD

From 41 patients who underwent primary total joint arthroplasties, peripheral blood samples were obtained at 1 day before (baseline) and 1, 3, 5, 7, and 14 days after surgery, and CD64 expression per cell was quantitatively measured. C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR) and white blood cell count (WBC) were simultaneously measured.

RESULTS

No cases of postoperative local infection were observed. Levels of CD64 significantly elevated from day 1, peaked at day 3, and decreased significantly following day 5. Statistical analysis confirmed that significant differences existed between the baseline level and the levels at days 1 and 3, while no significant differences existed between the baseline level and those at days 5, 7 or 14. In 17 patients, CD64 peaked at over 2,000 molecules/cell, the level reported to be a cutoff value for distinguishing infection. Multiple regression analysis showed that the sole parameter of baseline CD64 level significantly explained the peak CD64 level. Postoperative CD64 peaks ranged from 1.6 to 2.7 times (median 1.9) the baseline levels. CRP, ESR and WBC also showed rapid elevations and all but WBC remained significantly higher than baseline at day 14.

CONCLUSION

CD64 levels rise significantly, peaking within about 3 days following normal total joint arthroplasty, but decrease rapidly to near baseline within about 5 days. The data obtained can be expected to form a possible basis for early diagnosis of postoperative periprosthetic infection.

Neutrophil CD64 expression as a biomarker in the early diagnosis of bacterial infection: a meta-analysis

BACKGROUND

Neutrophil CD64 expression is widely reported as an efficacious biomarker to differentiate infected patients from other non-infected patients. This meta-analysis was conducted to comprehensively and quantitatively summarize the accuracy of neutrophil CD64 in the early diagnosis of bacterial infection.

METHODS

A systematic review of related studies was conducted, and the sensitivity, specificity, and other data about the accuracy of CD64 expression on neutrophils were pooled using random effects models with 95% confidence intervals (CI) as the effect measurements. Summary receiver operating characteristic (SROC) curves and the Q* value were also calculated in the meta-analysis. Heterogeneity was tested, as well as the publication bias. Potential sources of heterogeneity were explored by assessing whether or not certain covariates significantly influenced the summary diagnostic odds ratio (SDOR).

RESULTS

A total of 26 studies including 3944 patients met the inclusion criteria for the final analysis. The summary estimate was 0.76 (95% CI 0.74-0.78) for sensitivity and 0.85 (95% CI 0.83-0.86) for specificity. The positive likelihood ratio (PLR), negative likelihood ratio (NLR), SDOR, and area under the SROC of neutrophil CD64 expression with Q* value were 6.67 (95% CI 4.67-9.53), 0.24 (95% CI 0.18-0.31), 34.29 (95% CI 19.59-60.01), and 0.92 (Q*=0.85), respectively. The pooled data from the included studies had high heterogeneity and the Egger test suggested a publication bias.

CONCLUSIONS

On the basis of our meta-analysis, neutrophil CD64 expression could be a promising and meaningful biomarker for diagnosing bacterial infection. Nevertheless, more large prospective studies should be carried out before the neutrophil CD64 test is used widely in the clinical setting because of the various cut-off values.

Pyogenic discitis following discectomy

PURPOSE

To assess the treatment outcome for disc infection in 35 patients.

METHODS

Records of 23 men and 12 women aged 36 to 62 (mean, 43) years who underwent treatment for pyogenic discitis after open discectomy were reviewed. All patients had single-level disc herniation of L4-5 (n=28) or L5-S1 (n=6), except for one who had 2-level disc herniation of L4-S1. Single antibiotic was given one day prior to discectomy and continued for 2 days. All excised discs were found to be sterile. Discitis was classified into acute (n=26), subacute (n=7), and chronic (n=2). Antibiotic therapy was started immediately when the clinical diagnosis was made. 31 patients were treated with antibiotics alone; the remaining 4 underwent surgery entailing simple posterior superficial wound drainage (n=1), anterior radical surgery (n=2), or posterior instrumentation and posterolateral fusion for post-discectomy syndrome (n=1). Six of the 12 patients who had percutaneous disc space aspiration underwent disc space irrigation.

RESULTS

The initial symptoms included mild-to-moderate fever (n=4), severe back pain (n=27), back muscle spasms (n=26), back pain radiating to the limb (n=2), Gower sign (n=11), and a draining wound (n=1). The wound aspirates of the 12 patients grew organisms, although blood cultures were negative in all. After antibiotic therapy, symptoms gradually subsided in parallel with normalisation of white blood cell count and inflammatory markers. Surgery was indicated only when symptoms worsened and the disease progressed. Spontaneous intercorporal fusion did not occur.

CONCLUSION

Early diagnosis and treatment with appropriate antibiotics is important for post-discectomy discitis.

Simultaneous quantitative analysis of the expression of CD64 and CD35 on neutrophils as markers to differentiate between bacterial and viral infections in patients with rheumatoid arthritis

OBJECTIVES

The expression level of CD64 on neutrophils can be used to differentiate between an infection and a disease flare in rheumatoid arthritis (RA) patients. However, the CD64 expression is elevated by both bacteria and viruses, so it cannot be used to distinguish the type of infection. We herein investigated the results of a simultaneous quantitative analysis of the expression of CD64 and CD35 on neutrophils to determine whether these molecules can be used to distinguish between bacterial and viral infections in RA patients.

METHODS

We collected blood from 22 RA patients with pathogen-proven infections (15 bacterial and 7 viral infections). Blood samples were stained with QuantiBRITE CD64PE/CD45PerCP and CD35PE, and the mean fluorescence intensities were assessed by a flow cytometer. The mean numbers of molecules were calculated using QuantiBrite PE beads.

RESULTS

We calculated the ratio of CD64 to the CD35 level (CD35/CD64), and used a cut-off value of 2.8 for the CD35/CD64 ratio. At this value, the sensitivity for diagnosing a bacterial infection was 87%, and the specificity was 86%.

CONCLUSIONS

Simultaneous quantitative analysis of CD64 and CD35 expression on neutrophils might be useful to distinguish between bacterial and viral infections in RA patients.

Neutrophil CD64: diagnostic accuracy and prognostic value in patients presenting to the emergency department

The purpose of this study was to evaluate the diagnostic accuracy and prognostic value of neutrophil CD64 expression for bacterial infection in febrile adult patients presenting to our hospital emergency department. We prospectively included 132 patients with fever ≥ 38ºC (≥ 100.4ºF) during the last 24 hours and we measured CD64 expression on neutrophils the day after admission at the emergency department. We followed the patients until full recovery or death. There were 115 (87%) patients with bacterial infection and 108 (94%) of them survived. There were 17 (13%) patients without bacterial infection and 12 (71%) of them survived. Patients with bacterial infection and patients who survived showed a CD64 index higher when compared with patients without bacterial infection and patients who died, respectively (3.7 ± 3.2 vs. 2.5 ± 2.3; p = 0.03; and 3.7 ± 3.1 vs. 1.7 ± 0.6; p = 0.002; Mann-Whitney U test). The receiver operating characteristic (ROC) curve analysis for detecting bacterial infection and predicting survival with the CD64 index showed an area under curve (AUC) of 0.66 (95% CI, 0.52-0.8; p = 0.03) and 0.71 (95% CI, 0.57-0.85; p = 0.01), respectively. Diagnostic accuracy and prognostic value of CD64 expression was good in adult patients with fever.

The usefulness of neutrophil CD64 expression in the diagnosis of local infection in patients with rheumatoid arthritis in daily practice

BACKGROUND

The diagnosis of local infection in patients with rheumatoid arthritis (RA) is frequently difficult because clinical signs and symptoms and laboratory test results of local infection are also observed in arthritis of active RA. The need for a specific marker of infection is high in RA patients. The usefulness of neutrophil CD64 expression (CD64) to diagnose local musculoskeletal infection (local infection) and discriminate local infection from RA-related inflammation in RA patients was examined.

METHODS

CD64 was measured by a quantitative method using flow cytometry in 61 RA patients in whom local infection was suspected, and the usefulness of CD64 was examined by comparing the findings with clinical results.

RESULTS

There were 25 patients with local infection and 36 patients without infection. The median CD64 value the patients with local infection was 3148 molecules/cell (interquartile range [IQR], 2140-6231) and that of the patients without infection was 1106 molecules/cell (IQR, 804-1464) with a statistically significant difference (P < 0.0001). In contrast, no significant difference between the groups was observed in C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell (WBC) count. The area under the curve of CD64 calculated by receiver operating characteristic curve analysis was larger than that of CRP, ESR, or WBC count, suggesting that CD64 has superior ability to discriminate of infection compared to these other markers. When the cutoff value of CD64 was set at 2000 molecules/cell, the sensitivity and specificity of CD64 for the detection of local infection in RA patients were 76.0% and 94.4%, respectively.

CONCLUSIONS

CD64 is a useful marker in RA patients to discriminate local infection from RA-related inflammation.

Neutrophil CD64 expression as a diagnostic marker for local infection and crystal-induced arthritis

The usefulness of neutrophil CD64 expression was examined in diagnosing local infection, including soft tissue, bone, and joint infections. Among 99 patients suspected of local infection, 31 were confirmed and 68 patients were not. The CD64 level of patients with local infection was significantly higher than in those without infection [4,193 ± 1,132 vs. 1,017 ± 59 molecules/cell (mean ± standard deviation); p < 0.001]. The area under the curve of CD64 calculated by receiver operating characteristic curve analysis was larger than that of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), or white blood cell (WBC) count. In addition, CD64 levels of patients with crystal-induced arthritis remained within cutoff value (2,000 molecules/cell). These data suggest that measuring CD64 expression can be a useful diagnostic marker for local musculoskeletal infection and crystal-induced arthritis.

Neutrophil CD64 expression as marker of bacterial infection: a systematic review and meta-analysis

OBJECTIVE

We performed a systematic review and meta-analysis of studies to evaluate the diagnostic accuracy of expression of CD64 on polymorphonuclear neutrophils (PMN) as a marker for bacterial infection.

METHODS

The analysis included studies of patients from all age groups that prospectively evaluated CD64 expression on PMNs for the diagnosis of bacterial infection. We evaluated the methodological quality of the studies according to the 25-item criteria developed by the Standards for Reporting of Diagnostic Accuracy (STARD) committee. We calculated a summary receiver operating characteristic (SROC) curve across studies included in the meta-analysis.

RESULTS

The methodological quality score of the 13 included studies ranged from 9 to 16 points (maximum score was 25 points). The pooled sensitivity and specificity for CD64 expression on PMNs were 79% (95% CI: 70-86%) and 91% (95% CI: 85-95%), respectively. The area under curve (AUC) was 0.94.

CONCLUSIONS

On the basis of this meta-analysis, CD64 expression on PMNs could be a useful diagnostic cell-based parameter of bacterial infections. However, published studies about this topic showed a low methodological quality.