Derivation and validation of cutoffs for clinical use of cell cycle arrest biomarkers.

BACKGROUND: Acute kidney injury (AKI) remains a deadly condition. Tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein (IGFBP)7 are two recently discovered urinary biomarkers for AKI. We now report on the development, and diagnostic accuracy of two clinical cutoffs for a test using these markers. METHODS: We derived cutoffs based on sensitivity and specificity for prediction of Kidney Disease: Improving Global Outcomes Stages 2-3 AKI within 12 h using data from a previously published multicenter cohort (Sapphire). Next, we verified these cutoffs in a new study (Opal) enrolling 154 critically ill adults from six sites in the USA. RESULTS: One hundred subjects (14%) in Sapphire and 27 (18%) in Opal met the primary end point. The results of the Opal study replicated those of Sapphire. Relative risk (95% CI) in both studies for subjects testing at ≤0.3 versus >0.3-2 were 4.7 (1.5-16) and 4.4 (2.5-8.7), or 12 (4.2-40) and 18 (10-37) for ≤0.3 versus >2. For the 0.3 cutoff, sensitivity was 89% in both studies, and specificity 50 and 53%. For 2.0, sensitivity was 42 and 44%, and specificity 95 and 90%. CONCLUSIONS: Urinary [TIMP-2]•[IGFBP7] values of 0.3 or greater identify patients at high risk and those >2 at highest risk for AKI and provide new information to support clinical decision-making. CLINICAL TRIALS REGISTRATION: Clintrials.gov # NCT01209169 (Sapphire) and NCT01846884 (Opal).

Analytical and Clinical Performance Evaluation of the Elecsys HIV combi PT Assay on the cobas e 602 Analyzer for the Diagnosis of Human Immunodeficiency Virus.

OBJECTIVES: We evaluated the performance of the Elecsys HIV combi PT assay on the cobas e 602 analyzer for diagnosing human immunodeficiency virus (HIV; part of the US Food and Drug Administration [FDA] submission). METHODS: The HIV combi PT and reference (ARCHITECT HIV Ag/Ab Combo) assays were assessed at four independent clinical laboratories/one reference laboratory (United States; July 2014 to November 2015). Clinical performance was evaluated using four reagent lots. Analytical performance was evaluated per Clinical and Laboratory Standards Institute EP05-A3 guidelines. Serum/plasma samples from 18 clinical sites/vendors (United States and outside the United States) were tested. RESULTS: Sensitivity (95% confidence interval [CI]) in HIV-1 antibody-positive individuals (United States and outside the United States; n = 1,460) was 100.00% (99.75%-100.00%). Specificity was 99.94% (95% CI, 99.85%-99.98%) in low-risk individuals (United States; n = 6,843), 98.19% (95% CI, 96.93%-99.04%) in high-risk individuals (United States and outside the United States; n = 758), and 97.43% (95% CI, 95.32%-98.76%) in pregnant women (United States and outside the United States; n = 440). Analytical performance was acceptable. CONCLUSIONS: We demonstrate the robustness of the FDA-approved Elecsys HIV combi PT assay on the cobas e 602 analyzer for HIV testing in the United States.

Analytical characteristics of a biomarker-based risk assessment test for acute kidney injury (AKI).

BACKGROUND: Acute kidney injury (AKI) is associated with increased mortality, morbidity, hospital length of stay, and costs. A quantitative urine test is available to assess the risk of developing AKI by measuring the concentrations of two protein biomarkers, TIMP-2 and IGFBP-7. The NephroCheck Test combines these concentrations into an AKIRisk Score. The purpose of this study is to characterize the analytical performance characteristics of the AKIRisk Score. METHODS: Linearity and analytical sensitivity were evaluated by following Clinical Laboratory Standards Institute (CLSI) EP06-A and EP17-A, respectively. Precision was evaluated by testing clinical samples and examining the repeatability of test results. Potential interference was evaluated for endogenous and exogenous substances. Sample stability was examined at room temperature and at 2-8°C, as well as the effect of sample centrifugation temperature on test results. RESULTS: The AKIRisk Score exhibits approximately 10% coefficient of variation (CV) at the recommended cutoff value of 0.3 and the limit of quantitation (LoQ) was 0.002. Only albumin, bilirubin (conjugated), and methylene blue interfered with test results, at concentrations exceeding 1250 mg/L, 72 mg/L, and 0.49 mg/L, respectively. AKIRisk Score results were stable for 6h at room temperature, 24h refrigerated, and not impacted by sample centrifugation temperature. CONCLUSIONS: Our studies demonstrate that the AKIRisk Score has robust analytical performance, good precision, minimal analytical interference, acceptable sensitivity, and excellent sample stability.