Clinical chemistry
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The analytic performance and accuracy of drug detection below Substance Abuse and Mental Health Services Administration (SAMHSA) cutoffs is not well known. In some patient populations, clinically significant concentrations of abused drugs in urine may not be detected when current SAMHSA cutoffs are used. Our objectives were to define the precision profiles of three immunoassay systems for drugs of abuse and to evaluate the accuracy of testing at concentrations at which the CV was <20%. ⋯ The precision of three commercial immunoassay systems for drugs-of-abuse screening is adequate to detect drugs below SAMHSA cutoffs. Knowledge of the positive predictive values of screening immunoassays at lower cutoff concentrations could enable efficient use of confirmatory testing resources and improved detection of illicit drug use.
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The application of epidemiologic principles to clinical diagnosis has been less developed than in other clinical areas. Knowledge of the main flaws affecting diagnostic laboratory test research is the first step for improving its quality. We assessed the methodologic aspects of articles on laboratory tests. ⋯ The methodologic quality of the articles on diagnostic test research published in Clinical Chemistry and Clinical Chemistry and Laboratory Medicine is comparable to the quality observed in the best general medical journals. The methodologic aspects that most need improvement are those linked to the clinical information of the populations studied. Editorial actions aimed to increase the quality of reporting of diagnostic studies could have a relevant positive effect, as shown by the improvement observed in Clinical Chemistry.
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Circulating Epstein-Barr viral (EBV) DNA and anti-EBV capsid antigen IgA (IgA VCA) represent two of the most sensitive peripheral blood markers of nasopharyngeal carcinoma (NPC), but direct comparative studies of these two markers are lacking. ⋯ For diagnosis of NPC, EBV DNA identifies almost all false-negative IgA-VCA cases and gives a 99% diagnostic sensitivity when combined with IgA-VCA. In the screening setting, EBV DNA identifies three-fourths of false-positive IgA-VCA cases. The selective application of EBV DNA in an IgA-VCA-based screening protocol could improve screening accuracy with only moderate increases in cost.
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Cardiac troponin I (cTnI) is a more specific and sensitive biomarker than creatine kinase MB (CKMB) for detection of myocardial damage. We report the prevalence of positive cTnI and CKMB mass among patients hospitalized with suspected acute coronary syndrome (ACS) and the potential impact of use of different reference cutoffs, particularly those proposed by European Society of Cardiology/American College of Cardiology (ESC/ACC) consensus guidelines, on rates of diagnosis of acute myocardial infarction (AMI). ⋯ Use of lower reference cutoffs for plasma biomarkers, as recommended by ESC/ACC guidelines, markedly increases the rates of cTnI-positive cases overall. A substantial proportion of the increase in total cTnI-positive cases was derived from the creation of additional cTnI-positive/CKMB-negative cases. CKMB-positive/cTnI-negative cases are likely false positive for myocardial injury.