Prognostic Values of Platelet Distribution Width and Platelet Distribution Width-to-Platelet Ratio in Severe Burns

BACKGROUND

Platelet distribution width (PDW) and PDW-to-platelet ratio (PPR) have been proven to be good prognostic indicators for many diseases. However, their prognostic values in severe burns have not been reported.

OBJECTIVE

To investigate the early time course of PDW and PPR in severe burn patients and investigate their prognostic values.

METHODS

This is a 16-year, single-center retrospective study of 590 severe burn patients. The complete blood count parameters on day 1, day 3, and day 7 postburn, including PDW and PPR, were collected. Receiver operating characteristic curves (ROC) analysis, multiple logistic regression analysis and Kaplan-Meier survival analysis were performed to evaluate the prognostic values of PDW and PPR in severe burn patients.

RESULTS

According to 120-day follow-up records, 96 patients were nonsurvivors and 494 patients were survivors. ROC and area under the curve (AUC) analysis showed that, for predicting 120-day prognosis, the AUC of PDW (0.782) and PPR (0.816) on day 3 was the highest, followed by the AUC of PDW (0.764) and PPR (0.750) on day 7. The ROC-AUC of PPR (0.816) on day 3 was very close to that of the ABSI score (0.818). Multiple logistic regression analysis showed that the PDW (P = 0.033 and P = 0.009) and PPR (P = 0.052 and P = 0.046) on day 3 and day 7 were all significantly independently positively associated with 120-day mortality. Kaplan-Meier survival analysis showed that high PDW and PPR were both significantly associated with a high 120-day mortality rate on day 3 and day 7.

CONCLUSION

PDW and PPR on day 3 and day 7 were independent risk factors for 120-day mortality in severe burn patients. These objective and readily available prognostic indicators may be more clinically favored.

Red Cell Distribution Width at Admission Predicts the Frequency of Acute Kidney Injury and 28-Day Mortality in Patients With Acute Respiratory Distress Syndrome

OBJECTIVES

To determine the association of red cell distribution width (RDW) at admission with frequency of acute kidney injury (AKI) and 28-day mortality in acute respiratory distress syndrome (ARDS) patients.

METHODS

Two hundred fifty-eight ARDS patients were investigated in retrospective and prospective studies. The primary outcome was frequency of AKI. The secondary outcome was 28-day mortality.

RESULTS

The retrospective study included 193 ARDS patients, of which 67 (34.7%) were confirmed AKI and 76 (39.4%) died within 28 days. The RDW level in the AKI group was significantly higher than in the non-AKI group ([15.15 ± 2.59]% vs. [13.95 ± 1.89]%). Increased RDW was a significant predictor of frequency of AKI (odds ratio: 1.247, 95% confidence interval [CI]: 1.044, 1.489). The area under the receiver operating characteristic curve of RDW for predicting AKI was 0.687 (95%CI: 0.610, 0.764) and the cut-off value was 14.45 (sensitivity, 56.7%; specificity, 72.8%). In addition, the proportion of patients with RDW ≥ 14.45% in the non-survival group was notably higher compared with the survival group (48.7% vs. 29.1%). Furthermore, cox regression analysis revealed that RDW ≥ 14.45% was associated with 28-day mortality (hazard ratio: 1.817, 95%CI: 1.046, 3.158), while Kaplan-Meier analysis showed patients with RDW ≥ 14.45% had a significantly lower survival rate than those with RDW < 14.45%. The prospective study, on the other hand, included 65 ARDS patients, with frequency of AKI and 28-day mortality in the RDW ≥ 14.45% group significantly higher than in RDW < 14.45%.

CONCLUSION

RDW was a significant, independent predictor for frequency of AKI and 28-day mortality in ARDS patients.

Association of the Circulating Supar Levels with Inflammation, Fibrinolysis, and Outcome in Severe Burn Patients

BACKGROUND

Hyperfibrinolysis and pro/anti-inflammatory imbalance usually occur in the early stage of severe burns. Soluble urokinase-type plasminogen activator receptor (suPAR) is involved in fibrinolysis and inflammation. To date, the levels of circulating suPAR in non-survivors with severe burns remain unknown. This study aimed to investigate the early association between circulating suPAR levels and biomarkers of fibrinolysis, pro/anti-inflammatory, and prognosis.

METHODS

Sixty-four consecutive Chinese patients with severe burns and 26 healthy volunteers were enrolled in a prospective observational cohort. Clinical characteristics and laboratory data were collected prospectively. Blood samples were collected at 48 h post-burn, and suPAR and biomarkers of pro/anti-inflammatory and fibrinolysis were detected by enzyme-linked immunosorbent assays. Important indicators between non-survivors and survivors were compared. Linear regression analysis was performed to screen variables associated with suPAR. Logistic regression analysis and receiver operating characteristic curve (ROC) analysis were performed to evaluate the prognostic value of suPAR.

RESULT

Compared with the control group, the circulating suPAR levels in the survivors (P < 0.001) and non-survivors (P = 0.017) were higher. Compared with survivors, non-survivors had lower circulating suPAR levels at 48 h post-burn, and they showed a higher degree of fibrinolysis (higher D-dimer) and a lower TNF-α/IL-10 ratio. According to linear regression analysis, the variables independently associated with a lower suPAR level were lower platelet factor 4 (PF-4), urokinase-type plasminogen activator (uPA), and TNF-α/IL-10 levels and a higher D-dimer level. Logistic regression and ROC analyses indicated that a suPAR level ≤ 4.70 μg/L was independently associated with 30-day mortality.

CONCLUSION

Low circulating suPAR levels at 48 h post-burn in severe burn patients may reflect decreased TNF-α/IL-10 ratio and increased hyperfibrinolysis. suPAR can predict 30-day mortality in patients with severe burn.

Rhabdomyolysis is Associated with In-Hospital Mortality in Patients with COVID-19

PURPOSE

Rhabdomyolysis (RM) has been associated with many viral infectious diseases, and associated with poor outcomes. We aim to evaluate the clinical features and outcomes of RM in patients with coronavirus disease 2019 (COVID-19).

METHOD

This was a single-center, retrospective, cohort study of 1,014 consecutive hospitalized patients with confirmed COVID-19 at the Huoshenshan Hospital in Wuhan, China, between February 17 and April 12, 2020.

RESULTS

The overall incidence of RM was 2.2%. Compared with patients without RM, those with RM tended to have a higher risk of deterioration. Patients with RM also constituted a greater percentage of patients admitted to the intensive care unit (90.9% vs. 5.3%, P < 0.001) and a greater percentage of patients undergoing mechanical ventilation (86.4% vs. 2.7% P < 0.001). Moreover, patients with RM had laboratory test abnormalities, including the presence of markers of inflammation, activation of coagulation, and kidney injury. Patients with RM also had a higher risk of in-hospital death (P < 0.001). Cox's proportional hazard regression model analysis confirmed that RM indicators, including peak creatine kinase levels > 1,000 IU/L (HR = 6.46, 95% CI: 3.02-13.86) and peak serum myoglobin concentrations > 1,000 ng/mL (HR = 9.85, 95% CI: 5.04-19.28), were independent risk factors for in-hospital death. Additionally, patients with COVID-19 that developed RM tended to have delayed viral clearance.

CONCLUSION

RM might be an important contributing factor to adverse outcomes in COVID-19 patients. The early detection and effective intervention of RM may help reduce mortality among COVID-19 patients.

The Rate of Appropriate Adult Transthoracic Echocardiogram at King Abdulaziz University Hospital Based on Appropriate Use Criteria of 2011, 2017, and 2019

Background: Transthoracic echocardiography (TTE) is a basic method for cardiovascular disease diagnosis and treatment. Studies done to assess the appropriate use of TTE in the Kingdom of Saudi Arabia (KSA) are scarce.

Objectives: To assess the pattern of ordering TTE in King Abdulaziz University Hospital (KAUH) and the appropriateness of its ordering.

Methods: A retrospective study was done from October to November 2018 at KAUH, Echo lab, Jeddah City, KSA. Patients, more than 18 years who had TTE at KAUH were included.

Results: The criteria used were the 2019 criteria for most patients and the orders were appropriate for 77.9% of the 954 patients. Orders were significantly inappropriate for patients who had older age, and the number of indications were significantly higher for those whose orders were - "maybe appropriate" (M). The anesthesia department for outpatients and the surgical department for inpatients ordered a significantly high number of inappropriate requests. Inpatients had a significantly higher percentage of "appropriate" (A) orders, and a significant positive correlation was present between patients’ age and number of indications.

Conclusion: There is a need to maximize compliance with AUCs and its effect on clinical results should be evaluated.

Machine learning for genetic prediction of psychiatric disorders: a systematic review

Machine learning methods have been employed to make predictions in psychiatry from genotypes, with the potential to bring improved prediction of outcomes in psychiatric genetics; however, their current performance is unclear. We aim to systematically review machine learning methods for predicting psychiatric disorders from genetics alone and evaluate their discrimination, bias and implementation. Medline, PsycInfo, Web of Science and Scopus were searched for terms relating to genetics, psychiatric disorders and machine learning, including neural networks, random forests, support vector machines and boosting, on 10 September 2019. Following PRISMA guidelines, articles were screened for inclusion independently by two authors, extracted, and assessed for risk of bias. Overall, 63 full texts were assessed from a pool of 652 abstracts. Data were extracted for 77 models of schizophrenia, bipolar, autism or anorexia across 13 studies. Performance of machine learning methods was highly varied (0.48-0.95 AUC) and differed between schizophrenia (0.54-0.95 AUC), bipolar (0.48-0.65 AUC), autism (0.52-0.81 AUC) and anorexia (0.62-0.69 AUC). This is likely due to the high risk of bias identified in the study designs and analysis for reported results. Choices for predictor selection, hyperparameter search and validation methodology, and viewing of the test set during training were common causes of high risk of bias in analysis. Key steps in model development and validation were frequently not performed or unreported. Comparison of discrimination across studies was constrained by heterogeneity of predictors, outcome and measurement, in addition to sample overlap within and across studies. Given widespread high risk of bias and the small number of studies identified, it is important to ensure established analysis methods are adopted. We emphasise best practices in methodology and reporting for improving future studies.

ROC and AUC with a Binary Predictor: a Potentially Misleading Metric

In analysis of binary outcomes, the receiver operator characteristic (ROC) curve is heavily used to show the performance of a model or algorithm. The ROC curve is informative about the performance over a series of thresholds and can be summarized by the area under the curve (AUC), a single number. When a predictor is categorical, the ROC curve has one less than number of categories as potential thresholds; when the predictor is binary there is only one threshold. As the AUC may be used in decision-making processes on determining the best model, it important to discuss how it agrees with the intuition from the ROC curve. We discuss how the interpolation of the curve between thresholds with binary predictors can largely change the AUC. Overall, we show using a linear interpolation from the ROC curve with binary predictors corresponds to the estimated AUC, which is most commonly done in software, which we believe can lead to misleading results. We compare R, Python, Stata, and SAS software implementations. We recommend using reporting the interpolation used and discuss the merit of using the step function interpolator, also referred to as the "pessimistic" approach by Fawcett (2006).

Genetic Risk Scores

The generation of genome-wide variation data has become commonplace. However, the potential for interpretation and application of these data for clinical assessment of outcomes of interest, and prediction of disease risk, is currently not fully realized. Many common, complex diseases now have numerous, well-established "risk" loci, and likely harbor many genetic determinants with effects too small to be detected at genome-wide levels of statistical significance. A simple and intuitive approach for converting genetic data to a predictive measure of disease susceptibility is to aggregate the risk effects of these loci into a single genetic risk score. Here, some common methods and software packages for calculating genetic risk scores, with focus on studies of common, complex diseases, are described. The basic information needed as well as important considerations for constructing genetic risk scores, including specific requirements for phenotypic and genetic data, and limitations in their application is reviewed. © 2016 by John Wiley & Sons, Inc.

Searching for an optimal AUC estimation method: a never-ending task?

An effective method of construction of a linear estimator of AUC in the finite interval, optimal in the minimax sense, is developed and demonstrated for five PK models. The models may be given as an explicit C(t) relationship or defined by differential equations. For high variability and rich sampling the optimal method is only moderately advantageous over optimal trapezoid or standard numerical approaches (Gauss-Legendre or Clenshaw-Curtis quadratures). The difference between the optimal estimator and other methods becomes more pronounced with a decrease in sample size or decrease in the variability. The described estimation method may appear useful in development of limited-sampling strategies for AUC determination, as an alternative to the widely used regression-based approach. It is indicated that many alternative approaches are also possible.

AB127. Translation, adaptation and validation of Acute Cystitis Symptom Score’s German version

Introduction

Objectives

Materials and methods

Results

Conclusions

An analysis of 24-h ambulatory blood pressure monitoring data using orthonormal polynomials in the linear mixed model

BACKGROUND

The use of 24-h ambulatory blood pressure monitoring (ABPM) in clinical practice and observational epidemiological studies has grown considerably in the past 25 years. ABPM is a very effective technique for assessing biological, environmental, and drug effects on blood pressure.

OBJECTIVES

In order to enhance the effectiveness of ABPM for clinical and observational research studies using analytical and graphical results, developing alternative data analysis approaches using modern statistical techniques are important.

METHODS

The linear mixed model for the analysis of longitudinal data is particularly well suited for the estimation of, inference about, and interpretation of both population (mean) and subject-specific trajectories for ABPM data. We propose using a linear mixed model with orthonormal polynomials across time in both the fixed and random effects to analyze ABPM data.

RESULTS

We demonstrate the proposed analysis technique using data from the Dietary Approaches to Stop Hypertension (DASH) study, a multicenter, randomized, parallel arm feeding study that tested the effects of dietary patterns on blood pressure.

CONCLUSION

The linear mixed model is relatively easy to implement (given the complexity of the technique) using available software, allows for straightforward testing of multiple hypotheses, and the results can be presented to research clinicians using both graphical and tabular displays. Using orthonormal polynomials provides the ability to model the nonlinear trajectories of each subject with the same complexity as the mean model (fixed effects).

Understanding increments in model performance metrics

The area under the receiver operating characteristic curve (AUC) is the most commonly reported measure of discrimination for prediction models with binary outcomes. However, recently it has been criticized for its inability to increase when important risk factors are added to a baseline model with good discrimination. This has led to the claim that the reliance on the AUC as a measure of discrimination may miss important improvements in clinical performance of risk prediction rules derived from a baseline model. In this paper we investigate this claim by relating the AUC to measures of clinical performance based on sensitivity and specificity under the assumption of multivariate normality. The behavior of the AUC is contrasted with that of discrimination slope. We show that unless rules with very good specificity are desired, the change in the AUC does an adequate job as a predictor of the change in measures of clinical performance. However, stronger or more numerous predictors are needed to achieve the same increment in the AUC for baseline models with good versus poor discrimination. When excellent specificity is desired, our results suggest that the discrimination slope might be a better measure of model improvement than AUC. The theoretical results are illustrated using a Framingham Heart Study example of a model for predicting the 10-year incidence of atrial fibrillation.

Drug-containing gelatin treats as an alternative to gavage for long-term oral administration in rhesus monkeys (Macaca mulatta)

Long-term oral administration of immunosuppressive agents to transplanted rhesus monkeys (Macaca mulatta) is one of the major challenges in such studies. To avoid the drawbacks of gavage, we tested an alternative method for oral dosing of sirolimus in rhesus monkeys by adding sirolimus, a commonly used immunosuppressant, to gelatin to create drug-containing gelatin 'treats' that our macaques would accept voluntarily. We evaluated the oral bioequivalence of the oral solution and drug-containing gelatin and assayed the whole-blood levels of sirolimus after long-term drug delivery. We found that time to peak concentration but not peak concentration itself or the area under the time-concentration curve differed between the 2 groups. Although the maximal concentration data did not fit the condition of bioequivalence, those for the time-concentration curves from 0 to 24 h and from 0 h to infinity did; therefore the extent of sirolimus absorption did not differ significantly between the 2 formulations. The sirolimus levels for long-term drug delivery were equivalent at 2.97 ± 1.91 ng/mL in the gelatin group and 3.13 ± 2.03 ng/mL in the solution group. The gelatin dosing technique we describe here is convenient and effective for oral administration of sirolimus in rhesus monkeys and likely can be adapted for other drugs.

On Efficient Assessment of Image-Quality Metrics Based on Linear Model Observers

This paper is motivated by the problem of image-quality assessment using model observers for the purpose of development and optimization of medical imaging systems. Specifically, we present a study regarding the estimation of the receiver operating characteristic (ROC) curve for the observer and associated summary measures. This study evaluates the statistical advantage that may be gained in ROC estimates of observer performance by assuming that the difference of the class means for the observer ratings is known. Such knowledge is frequently available in image-quality studies employing known-location lesion detection tasks together with linear model observers. The study is carried out by introducing parametric point and confidence interval estimators that incorporate a known difference of class means. An evaluation of the new estimators for the area under the ROC curve establishes that a large reduction in statistical variability can be achieved through incorporation of knowledge of the difference of class means. Namely, the mean 95% AUC confidence interval length can be as much as seven times smaller in some cases. We also examine how knowledge of the difference of class means can be advantageously used to compare the areas under two correlated ROC curves, and observe similar gains.

Predictive performance of prostate cancer risk in Chinese men using 33 reported prostate cancer risk-associated SNPs

BACKGROUND

Genome-wide association studies (GWAS) have identified more than 30 single nucleotide polymorphisms (SNPs) that were reproducibly associated with prostate cancer (PCa) risk in populations of European descent. In aggregate, these variants have shown potential to predict risk for PCa in European men. However, their utility for PCa risk prediction in Chinese men is unknown.

METHODS

We selected 33 PCa risk-related SNPs that were originally identified in populations of European descent. Genetic scores were estimated for subjects in a Chinese case-control study (1,108 cases and 1,525 controls) based on these SNPs. To assess the performance of the genetic score on its ability to predict risk for PCa, we calculated area under the curve (AUC) of the receiver operating characteristic (ROC) in combination with 10-fold cross-validation.

RESULTS

The genetic score was significantly higher for cases than controls (P = 5.91 × 10(-20)), and was significantly associated with risk of PCa in a dose-dependent manner (P for trend: 4.78 × 10(-18)). The AUC of the genetic score was 0.604 for risk prediction of PCa in Chinese men. When ORs derived from this Chinese study population were used to calculate genetic score, the AUCs were 0.631 for all 33 SNPs and 0.617 when using only the 11 significant SNPs.

CONCLUSION

Our results indicate that genetic variants related to PCa risk may be useful for risk prediction in Chinese men. Prospective studies are warranted to further evaluate these findings.

Joint analysis of multiple biomarkers for identifying type 2 diabetes in middle-aged and older Chinese: a cross-sectional study

OBJECTIVE

Identifying individuals with high risk of type 2 diabetes is important. To evaluate discriminatory ability of multiple biomarkers for type 2 diabetes in a Chinese population.

METHODS

Plasma adiponectin, plasminogen activator inhibitor-1, retinol-binding protein 4, resistin, C-reactive protein, interleukin 6 (IL-6), tumour necrosis factor α receptor 2 and ferritin were measured in a population-based sample of 3189 Chinese (1419 men and 1770 women) aged 50-70 years. A weighted biomarkers risk score (BRS) was developed based on the strength of associations of these biomarkers with type 2 diabetes. The discriminatory ability was tested by the area under receiver operating characteristics curve (AUC).

RESULTS

Adiponectin, plasminogen activator inhibitor-1, IL-6 and ferritin were independently associated with the prevalence of type 2 diabetes, and they were used to calculate the biomarkers risk score (BRS). After adjustment for the confounding factors, the ORs for type 2 diabetes and impaired fasting glucose with each point increment of BRS were 1.28 (95% CI 1.22 to 1.34) and 1.16 (1.12 to 1.20), respectively. Compared with those in the lowest quintile of the BRS, the participants in the highest quintile have an OR (95% CI) of 6.67 (4.21 to 10.55) for type 2 diabetes. The area under the curve for the BRS and conventional risk factors alone was 0.73 and 0.76, respectively, and substantially increased to 0.81 after combining both BRS and conventional risk factors (p<0.001).

CONCLUSIONS

These data suggest that combining multiple biomarkers and conventional risk factors might substantially enhance the ability to identify individuals with type 2 diabetes. More prospective data are warranted to confirm this observation.

Pharmacokinetics of cefovecin in cynomolgus macaques (Macaca fascicularis), olive baboons (Papio anubis), and rhesus macaques (Macaca mulatta)

Cefovecin sodium is a long-acting, third-generation, cephalosporin antibiotic approved for the treatment of skin infections in dogs and cats. The pharmacokinetic properties of cefovecin were evaluated in cynomolgus macaques (Macaca fascicularis), olive baboons (Papio anubis), and rhesus macaques (Macaca mulatta) by using a single-dose (8 mg/kg SC) dosing regimen. Plasma cefovecin concentrations were determined by using ultra-performance liquid chromatography with tandem mass spectrometry, and a noncompartmental model was used to determine pharmacokinetic parameters. The half-life of cefovecin was 4.95 ± 1.47 h in cynomolgus macaques, 9.17 ± 1.84 h in olive baboons, and 8.40 ± 2.53 h in rhesus macaques. These values are considerably lower than the half-lives previously published for dogs (133 h) and cats (166 h). The extended half-life of cefovecin in dogs and cats is speculated to be due to active reabsorption of drug in the kidney tubules because plasma clearance is well below the normal glomerular filtration rate. In nonhuman primates, renal clearance rates approximated plasma clearance rates, suggesting that active renal reabsorption of cefovecin does not occur in these species. The pharmacokinetic properties of cefovecin in nonhuman primates are vastly different from the pharmacokinetic properties in dogs and cats, precluding its use as a long-acting antibiotic in nonhuman primates. This study highlights the importance of performing pharmacokinetic studies prior to extralabel drug usage.

Self-association studies of the bifunctional N-acetylglucosamine-1-phosphate uridyltransferase from Escherichia coli

The N-acetylglucosamine-1-phosphate uridyltransferase (GlmU) is a key bifunctional enzyme in the biosynthesis of UDP-GlcNAc, a precursor in the synthesis of cell wall peptidoglycan. Crystal structures of the enzyme from different bacterial strains showed that the polypeptide forms a trimer through a unique parallel left-handed beta helix domain. Here, we show that the GlmU enzyme from Escherichia coli forms a hexamer in solution. Sedimentation equilibrium analytical ultracentrifugation demonstrated that the enzyme is in a trimer/hexamer equilibrium. Small-angle X-ray scattering studies were performed to determine the structure of the hexameric assembly and showed that two trimers assemble through their N-terminal domains. The interaction is mediated by a loop that undergoes a large conformational change in the uridyl transferase reaction, a feature that may affect the enzymatic activity of GlmU.

Solution structure and characterisation of the human pyruvate dehydrogenase complex core assembly

Mammalian pyruvate dehydrogenase complex (PDC) is a key multi-enzyme assembly that is responsible for glucose homeostasis maintenance and conversion of pyruvate into acetyl-CoA. It comprises a central pentagonal dodecahedral core consisting of two subunit types (E2 and E3BP) to which peripheral enzymes (E1 and E3) bind tightly but non-covalently. Currently, there are two conflicting models of PDC (E2+E3BP) core organisation: the 'addition' model (60+12) and the 'substitution' model (48+12). Here we present the first ever low-resolution structures of human recombinant full-length PDC core (rE2/E3BP), truncated PDC core (tE2/E3BP) and native bovine heart PDC core (bE2/E3BP) obtained by small-angle X-ray scattering and small-angle neutron scattering. These structures, corroborated by negative-stain and cryo electron microscopy data, clearly reveal open pentagonal core faces, favouring the 'substitution' model of core organisation. The native and recombinant core structures are all similar to the truncated bacterial E2 core crystal structure obtained previously. Cryo-electron microscopy reconstructions of rE2/E3BP and rE2/E3BP:E3 directly confirm that the core has open pentagonal faces, agree with scattering-derived models and show density extending outwards from their surfaces, which is much more structurally ordered in the presence of E3. Additionally, analytical ultracentrifugation characterisation of rE2/E3BP, rE2 (full-length recombinant E2-only) and tE2/E3BP supports the substitution model. Superimposition of the small-angle neutron scattering tE2/E3BP and truncated bacterial E2 crystal structures demonstrates conservation of the overall pentagonal dodecahedral morphology, despite evolutionary diversity. In addition, unfolding studies using circular dichroism and tryptophan fluorescence spectroscopy show that the rE2/E3BP is less stable than its rE2 counterpart, indicative of a role for E3BP in core destabilisation. The architectural complexity and lower stability of the E2/E3BP core may be of benefit to mammals, where sophisticated fine-tuning is required for cores with optimal catalytic and regulatory efficiencies.

Population analysis of a 24-h paclitaxel infusion in advanced endometrial cancer: a gynaecological oncology group study

AIMS

To examine determinants of paclitaxel disposition and the association between paclitaxel exposure and toxicity or survival in patients with advanced stage or recurrent endometrial cancer treated with doxorubicin plus paclitaxel.

METHODS

A limited sampling scheme was used to examine the population pharmacokinetics of paclitaxel in 160 patients from one arm of a randomized Phase III trial of doxorubicin plus paclitaxel or cisplatin. Four plasma samples per patient were collected at approximately 0, 3, 22 and 27 h after the first 24-h infusion of paclitaxel and submitted to the Gynecological Oncology Group (GOG) Pharmacology Core Laboratory. Total paclitaxel concentrations were quantified by LC/MS and paclitaxel disposition was examined using NONMEM. Paclitaxel exposure was evaluated for associations with toxicity or survival.

RESULTS

Patient weight, age and serum glutamic-oxaloacetic transaminase level were determinants of paclitaxel clearance (clearance increased 0.437 l h-1 kg-1; decreased 0.223 l h-1 year-1 and 0.105 l h-1 IU-1). Bayesian shrinkage was minimal for this parameter. In different measures of paclitaxel exposure, AUC was most predictive of toxicity, with higher AUC associated with granulocytopenia [probability of 1% at AUC=1 to 22% at AUC=4 microg l-1 h-1 for performance status (PS)=0]. PS was more strongly associated with survival than disease stage and higher paclitaxel AUC was associated with worse survival irrespective of PS and stage.

CONCLUSIONS

Paclitaxel AUC is an independent predictor of granulocytopenia and survival in patients with advanced stage or recurrent endometrial cancer. Future studies are needed to validate the latter finding. This study confirms the appropriateness of evaluating pharmacokinetics and pharmacodynamics in multicentre oncology trials.

Pharmacokinetics and pharmacodynamics of low-dose methotrexate in the treatment of psoriasis

AIMS

The aim of this 13 week, randomized, parallel-group study was to evaluate the relationship between the pharmacokinetics (PK) and pharmacodynamics (PD) of low-dose intermittent oral methotrexate (LDMTX) in patients with psoriasis.

METHODS

Twenty-four psoriatic patients (15 male and 9 female, aged 31-73 years) were given weekly doses of MTX doses of either 7.5 mg or 15 mg with each dose divided into three aliquots given at 12 h intervals. The pharmacokinetics of MTX were evaluated at weeks 1 and 13. Skin impairment was assessed using the PASI-scoring system (The Psoriasis Area and Severity Index) at baseline and at weeks 5, 9 and 13 of therapy. Haematological and biochemistry tests were also performed at these times.

RESULTS

The comparison of the areas under the plasma concentration-time curve (AUC(MTX)) after the first and third weekly doses showed that the extent of MTX accumulation in plasma was only about 12%. Two-way anova (factors: subject and the week of therapy) on the log-transformed AUC(MTX) showed no effect of the week of therapy (P>0.8). Moreover, the intraindividual variability in the AUC(MTX) was at least 4-fold less than the interindividual variability (F-test; P<0.01). The steady-state total plasma clearance of MTX ranged from 5.0 to 18.2 l h(-1) and was proportional to the renal clearance (r2=0.45, P<0.001) which accounted for 65+/-20% of the former. The renal clearance of 7-OHMTX was approximately 4-8% of that of the parent compound. PK/PD analysis revealed a highly significant inverse relationship between PASI (expressed as a percent of the initial value) and a steady-state AUC(MTX) (rs=-0.65, P<0.001). Seventeen subjects (8 from the 7.5 mg group and 9 from the 15 mg group MTX, P=0.67) achieved a greater than 50% decrease in the initial PASI score and were classified as responders. Thirteen of 14 subjects with AUC(24,36 h)> or =700 nmol l(-1) h responded to pharmacotherapy. Conversely, only 4 out of 10 subjects with AUC(24,36 h)<700 nmol l-1 h were responders (P<0.01, Fisher's exact test).

CONCLUSIONS

A strong correlation was observed between the pharmacokinetics (AUC(MTX) at the steady state) and antipsoriatic effect (PASI-score) of LDMTX. The considerable interindividual variability and low intraindividual variability in MTX pharmacokinetics support a role for therapeutic monitoring and dose individualization at the start of pharmacotherapy. The results of this study suggest that a steady state AUC(MTX) values of 700 nmol l(-1)h and higher are associated with a significantly better success rate of antipsoriatic therapy than lower values.

Close correlation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate, an intracellular active metabolite, to the therapeutic efficacy of N(4)-behenoyl-1-beta-D-arabinofuranosylcytosine therapy for acute myelogenous leukemia

N(4)-Behenoyl-1-beta-D-arabinofuranosylcytosine (BHAC), a prodrug of 1-beta-D-arabinofuranosylcytosine, is used effectively for the treatment of leukemia in Japan. BHAC therapy may be more effective if it is delivered in conjunction with monitoring of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP), the intracellular active metabolite of ara-C derived from BHAC. However, previous monitoring methods for ara-CTP were insufficiently sensitive. Here, using our new sensitive method, we evaluated the ara-CTP pharmacokinetics in relation to the therapeutic response in 11 acute myelogenous leukemia patients who received a 2-h infusion of BHAC (70 mg / m(2)) in combination remission induction therapy. ara-CTP could be monitored at levels under 1 mM. BHAC maintained effective levels of plasma ara-C and intracellular ara-CTP for a longer time, even compared with historical values of high-dose ara-C. The area under the concentration-time curve of ara-CTP was significantly greater in the patients with complete remission than in the patients without response. This greater amount of ara-CTP was attributed to the higher ara-CTP concentrations achieved in the responding patients. There was no apparent difference of plasma ara-C pharmacokinetics between the two groups. Thus, for the first time, the ara-CTP pharmacokinetics was evaluated in relation to the therapeutic effect of BHAC, and the importance of ara-CTP was proven. Administration of optimal BHAC therapy may require monitoring of the ara-CTP pharmacokinetics in each individual patient.

Plasma level monitoring of nasal salmon calcitonin in the rat by a heterogeneous two-site enzyme immunoassay

The experimental and clinical effectiveness of nasal salmon calcitonin (SCT) for treatment of osteoporosis in humans has been well established, but none is known yet about the pharmacokinetic property in relation to therapeutic efficacy, especially when used in a therapeutic dose range. This preclinical study was designed to evaluate such a property, first of all in rats, using a novel heterogeneous two-site enzyme immunoassay that has allowed us to evaluate the pharmacokinetic property of parenteral SCT in rats due to the high sensitivity (the detection limit = 2 pg of SCT/ml of plasma). It was found that as early as 10 min after the nasal dosing of 1.25, 5, or 20 U/rat, the SCT immunoactivity became detectable in plasma and thereafter it waned rapidly with time. Hypocalcemia developed in a dose-dependent manner, but with a delay of approximately 20 min from the peak of the immunoactivity and lasted hours. The pharmacokinetic parameters measured for the doses (1.25, 5, and 20 U/rat) were as follows; the AUCs (pg.hr/ml) = 20.8, 89.0, and 189, and the MRTs (min) = 52, 54, and 45, respectively. The results appear to suggest: (1) the unexpected quick transfer of nasal SCT into and from the circulation, (2) a delayed onset of hypocalcemia and possibly its anti-osteopenic action, both of which may last longer, (3) that keeping the plasma SCT above the in vitro anti-osteoclastic level (approximately 1 pM) only for a few hours per 2 days would be enough for inducing the distinct anti-osteopenic effect in rats, and (4) the feasibility of designing the clinical study as to the pharmacokinetics and pharmacodynamics of nasal SCT on humans.

A pharmacokinetic and pharmacodynamic analysis of CPT-11 and its active metabolite SN-38

In the present study, an attempt was made to determine the precise pharmacokinetics of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). The relationship between pharmacokinetic parameters and pharmacodynamic effects was also investigated to elucidate the cause of interpatient variation in side effects. Thirty-six patients entered the study. CPT-11, 100 mg/m2, was administered by IV infusion over 90 min weekly for four consecutive weeks. The major dose-limiting toxicities were leukopenia and diarrhea. There was a positive correlation between the area under the concentration-time curve (AUC) of CPT-11 and percent decrease of WBC (r = 0.559). On the other hand, episodes of diarrhea had a better correlation with the AUC of SN-38 (r = 0.606) than that of CPT-11 (r = 0.408). Multivariate analysis revealed that the AUC of SN-38, AUC of CPT-11 and indocyanine green retention test were significant variables for the incidence of diarrhea and that both performance status and AUC of CPT-11 were significant variables for percent decrease of WBC. The large interpatient variability of the degree of leukopenia and diarrhea is due to a great plasma pharmacokinetic variation in CPT-11 or SN-38. The AUCs of CPT-11 and SN-38 obtained from the first administration of CPT-11 correlate with toxicities, but it is impossible to predict severe side effects before the administration of CPT-11 at the present time.

A limited sampling model for estimating pharmacokinetics of CPT-11 and its metabolite SN-38

The objective of this study was to develop a limited sampling model (LSM) to estimate the area under the curve (AUC) of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and that of 7-ethyl-10-hydroxycamptothecin (SN-38) as predictive pharmacokinetic variables for leukopenia and episodes of diarrhea induced by CPT-11 administration. The model was developed with a training set consisting of pharmacokinetic studies in 36 patients who received a 90-min i.v. infusion of CPT-11 at a dose of 100 mg/m2. A multiple regression analysis of CPT-11 or SN-38 concentrations observed at each time point in the training set was used to predict the AUC of CPT-11 or SN-38. The final sampling models using only two time points were: AUCCPT-11 = 3.7891*C2.5 + 14.0479*C13.5 + 1.5463 AUCSN-38 = 0.5319*C2.5 + 19.1468*C13.5 + 72.7349 where C2.5 and C13.5 are the plasma concentration of CPT-11 (micrograms/ml) or SN-38 (ng/ml) at 2.5 and 13.5 h after the initiation of CPT-11 infusion, respectively. The models were validated prospectively on a separate test data set of 12 patients receiving the same dose of CPT-11 investigated in a previous study. Validation of the final LSM on the test data set gave values of root mean square error (RMSE) of 12.72% and 5.97% for the AUC of CPT-11 and that of SN-38, respectively. The model can be used to monitor the AUCs of both CPT-11 and SN-38 for the early prediction of toxicities and to establish a pharmacokinetically based dose modification strategy for safe administration of CPT-11.