Assessment of diagnostic tests to inform policy decisions--visual electrodiagnosis.

OBJECTIVES: To conduct a systematic review of the evidence for the effectiveness of five visual electrodiagnostic tests to inform the Medical Services Advisory Committee (MSAC) of the Department of Health and Ageing (Australia) in its decision in allocating public funding for new technologies. METHODS: We searched the biomedical literature to identify English-language articles published from 1966 to September 2000. We assessed validity of methodology of included studies against the following criteria: investigators (i) compared test with an appropriate reference test; (ii) tested an appropriate spectrum of patients; (iii) masked assessment of study and reference tests; (iv) measured the study test independently of clinical information; and (v) measured the reference test before any interventions. RESULTS: Sixty-one articles met inclusion criteria for critical appraisal: nineteen were cross-sectional studies that compared a study test with another test, thirty-four were case-control studies that compared a test in a group of patients with an eye disease to a group of subjects without eye disease, and eight studies were case series. None of the included studies met all of the validity criteria. Only four studies provided enough information to calculate diagnostic characteristics but were flawed due to inclusion of patients already diagnosed with disease or lack of an appropriate reference test and, thus, overestimated test accuracy. CONCLUSIONS: Identified studies did not provide sufficient valid evidence of the clinical value of the five visual tests in diagnosing diseases of the retina or optic nerve. Thus, MSAC recommended that the tests not be supported by public funding.