Three tests (A, B and C) for the diagnosis of breast cancer in premenopausal women were assessed against a ‘gold standard’ taken to be 100%

accurate. Their sensitivities were A 90%, B 85%, C 80%. Their specifi cities were A 100%, B 90%, C 95%. All three tests carried the same cost, and none was associated with any side-effects. It follows that:

(a) In these circumstances test A will always be preferable to test B.

(b) In these circumstances test B will always be preferable to test C.

(c) Test B detects a higher proportion of cases than test C.

(d) There are no false positive results with test A.

(e) The predictive value of test B will depend on the prevalence of disease in the population to which it is applied.