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 LFTs in patients with hypertension and determine downstream consequences of testing. Design & setting: Prospective study using the Clinical Practice Research Datalink (CPRD). Method: In total, 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 6 months following testing were measured. Results: The 1-year incidence of liver disease in patients with hypertension was 0.5% (95% confidence interval [CI] = 0.4% to 0.6%). Sensitivity and specificity of an LFT panel were modest: 61.3% (95% CI = 53.1% to 69.0%) and 73.8% (95% CI = 73.1% to 74.3%), respectively. The positive predictive value (PPV) 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: PPVs of LFTs in primary care were low, with high rates of false-positive results and increased rates of subsequent consultations, referrals, and blood testing. Avoiding LFTs for routine monitoring could potentially reduce patients’ anxiety, GP workload, and healthcare costs.