ITEM 8. Describe technical specifications of material and methods involved including how and when measurements were taken, and/or cite references for index tests and reference standard.
Concentrations of prostate-specific antigen (PSA) were measured by the Tandem total PSA and free PSA monoclonal antibody-based assays (Hybritech).[ref] A new, time-resolved immunofluorometric assay, recently developed in our laboratory, was used to measure serum hK2 concentrations.[ref] Briefly, the hK2 assay uses a mouse monoclonal anti-hK2 capture antibody [coded G586, supplied by Hybritech (San Diego, CA)and raised against recombinant hK2], a biotinylated mouse monoclonal detection antibody (coded 8311; Diagnostic Systems Laboratories) and alkaline phosphatase-labeled streptavidin. We measured the alkaline phosphatase activity by adding the substrate diflunisal phosphate, incubating for 10 min, and then adding a Tb 3+ -EDTA developing solution. The fluorescence was measured on a Cyberfluor 615 Immunoanalyzer (MDS Nordion). The hK2 assay has a detection limit of 0.006 µg/L and has <0.2% cross-reactivity to PSA. A full description of the method and its evaluation has been published elsewhere.
Authors should describe the methods involved in the execution of index test and reference standard in sufficient detail to allow other researchers to replicate the study or to allow readers to judge the feasibility of the index test in their own setting. Differences in the execution of the index test and reference standard are a potential source of variation in diagnostic accuracy.[2,3]
The description should cover the full test protocol including the specification of materials and instruments together with their instructions for use, and specific measures (preparations) in participants (e.g. fasting prior to blood sampling, the anatomic site of measurement). If no citations are available, details must be provided in the text. Between-study variability in measures of test accuracy due to differences in test protocol has been documented for a number of tests, including the use of hyperventilation prior to exercise electrocardiography and the use of tomography for exercise thallium scintigraphy.[3,4]
Magklara A, Scorilas A, Catalona WJ, Diamandis EP. The combination of human glandular kallikrein and free prostate-specific antigen (PSA) enhances discrimination between prostate cancer and benign prostatic hyperplasia in patients with moderately increased total PSA. Clin Chem 1999;45: 1960-6.
Irwig LM, Bossuyt PM, Glasziou PP, Gatsonis C, Lijmer JG. Designing studies to ensure that estimates of test accuracy will travel. In: Knottnerus JA, ed. The evidence base of clinical diagnosis. London: BMJ Publishing Group, 2002:95-116.
Detrano R, Gianrossi R, Froelicher V. The diagnostic accuracy of the exercise electrocardiogram: a meta-analysis of 22 years of research. Prog Cardiovasc Dis 1989; 32:173-206.
Philbrick JT, Horwitz RI, Feinstein AR. Methodologic problems of exercise testing for coronary artery disease: groups, analysis and bias. Am J Cardiol 1980; 46:807-12.