Liver function tests in patients with hypertension in primary care: a prospective cohort study

Abstract
Background Liver Function Tests (LFTs) are frequently used to monitor patients with hypertension in UK primary care. Evidence is lacking on whether testing improves outcomes.

Aim To estimate the diagnostic accuracy of LFT in patients with hypertension and determine downstream consequences of testing.

Design & Setting Prospective study using the Clinical Practice Research Database (CPRD).

Method 30,000 patients with hypertension who had LFTs in 2015 were randomly selected from CPRD. The diagnostic accuracy measures for eight LFT analytes and an overall LFT panel were calculated against the reference standard of liver disease. Rates of consultations, blood tests and referrals within six months following testing were measured.

Results The one-year incidence of liver disease in patients with hypertension was 0.5% (95% CI 0.4% to 0.6%). Sensitivity and specificity of an LFT panel were modest: 61.3% (53.1% to 69.0%) and 73.8% (73.1% to 74.3%), respectively. The positive predictive value of the eight individual LFT analytes were low ranging from 0.2% to 8.9%. Among patients who did not develop liver disease, mean number of consultations, referrals and tests were higher in the 6 months following false positives at 10.5, 0.7 and 29.8 respectively, compared with true negatives: 8.6, 0.6, and 19.8.

Conclusion Positive predictive values of LFT in primary care were low, with high rates of false positive results and increased rates of subsequent consultations, referrals, and blood testing. Avoiding LFT for routine monitoring could potentially reduce patient’s anxiety, GP workload, and healthcare costs.