Estimating the diagnostic accuracy of XXXX factor in UK primary care: a study using the Clinical Practice Research Datalink.

@entity1 @entity85 @entity309 @entity6470
OBJECTIVE: To investigate the diagnostic accuracy of @entity6470 as a test for @entity309 in primary care and its impact on referral times using the Clinical Practice Research Datalink. METHODS: We identified all @entity1 with a first @entity6470 test recorded in the Clinical Practice Research Datalink between 1 January 2000 and 31 December 2008 and those diagnosed with @entity309 within 2 years of testing. We calculated likelihood ratios (LRs), sensitivity, specificity and predictive values of @entity6470 for a diagnosis of @entity309 . We compared time to hospital referral in those testing positive and negative using Kaplan-Meier failure curves and log-rank tests. RESULTS: Of 62 436 first @entity6470 tests, 4679 (7.5%) were positive. There were 1753 incident cases of @entity309 , of which 57.8% were seropositive. The positive LR for @entity6470 was 9.5 (95% CI 9.0, 10.0) and the negative LR was 0.5 (95% CI 0.4, 0.5). Sensitivity and specificity were 57.8% (95% CI 55.4%, 60.1%) and 93.9% (95% CI 93.7%, 94.1%) and the positive predictive value and negative predictive value were 21.4% (95% CI 20.3%, 22.6%) and 98.7% (95% CI 98.6%, 98.8%), respectively. Median time to first hospital contact after the first @entity6470 test in those with seropositive vs seronegative results was 54 days (95% CI 49, 58) vs 150 (95% CI 147, 152). CONCLUSION: Only 2.8% of @entity1 undergoing @entity6470 testing were diagnosed with @entity309 , suggesting that @entity6470 is used to screen @entity1 with @entity85 rather than those with more specific features of @entity309 . A positive @entity6470 test may be helpful in diagnosing @entity309 in primary care but performs badly in excluding @entity309 and may delay referral.
