Assessing the impact of biomarkers on patient outcome: An obligatory step

Figures & data

Table I. Common test characteristics that are amenable to study.

Analytical characteristics	Bias, imprecision, detection limit, limit of quantification
Nonanalytical/biological factors	Biological variation, sample stability, etc.
Diagnostic and prognostic accuracy	Likelihood ratio, sensitivity/specificity, predictive value, etc.
Outcomes of testing	Examples: Morbidity, mortality, length of stay in hospital, readmission rates
Economic impacts	Examples: Cost-benefit, cost-effectiveness, cost-utility, and others

Table II. Examples of test attributes and outcomes that are amenable to study in outcomes studies.

Test attribute	Outcome
Availability/non availability of test	Mortality, morbidity
Method of testing	Patients' satisfaction with care
Turnaround time for test	Length of stay
Bias of test	Readmission rate
Method of reporting, e.g., with or without test interpretation	Complication rate

Table III. Problems in the performance of outcomes studies of diagnostic tests.

Remoteness of outcome from performance of test

Inconsistent response of physicians to results of test

High cost of studies relative to potential financial profit to corporate funders

Risk of loss of financial profits if favourable outcomes are not achieved

Limited perceived savings to health insurers or government that fund studies

Large required number of patients/volunteers (sample size)

Reluctance to withhold accepted test to do comparative trial

Confounding

Limited ability to conceal identity of tested vs not-tested participants

Concealment of allocation

Table IV. Guidance on performance of test evaluations.

Analytical evaluations:	Textbooks of clinical chemistry/laboratory medicine Information for authors of Clinical Chemistry
Preanalytical effects:	Publications of Harris, Fraser, et al.
Diagnostic accuracy:	STARD: Standards for reporting diagnostic accuracy
Outcomes studies:	Consolidated standards on reporting trials: CONSORT [7]

Begg C, Cho M, Eastwood S, Horton R, Moher D, Olkin I, . Improving the quality of reporting of randomized controlled trials. The CONSORT statement. JAMA 1996;276: 637–9.

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