Urinary beta-2 microglobulin and alpha-1 microglobulin are useful screening markers for tenofovir-induced kidney tubulopathy in patients with HIV-1 infection: a diagnostic accuracy study

Kidney tubulopathy is a well-known adverse event of antiretroviral agent tenofovir. A cross-sectional study was conducted to compare the diagnostic accuracy of five tubular markers, with a collection of abnormalities in these markers as the reference standard. The study subjects were patients with HIV-1 infection on ritonavir-boosted darunavir plus tenofovir/emtricitabine with suppressed viral load. Kidney tubular dysfunction (KTD) was predefined as the presence of at least three abnormalities in the following five parameters: β2-microglobulinuria (β2M), α1-microglobulinuria (α1M), high urinary N-acetyl-β-d-glucosaminidase (NAG), fractional excretion of phosphate (FE_IP), and fractional excretion of uric acid (FE_UA). Receiver operating characteristic curves and areas under the curves (AUC) were estimated, and the differences between the largest AUC and each of the other AUCs were tested using a nonparametric method. The cutoff value of each tubular marker was determined using raw data of 100 % sensitivity with maximal specificity. KTD was diagnosed in 19 of the 190 (10 %) patients. The AUCs (95 % CIs) of each tubular marker were β2M, 0.970 (0.947–0.992); α1M, 0.968 (0.944–0.992); NAG, 0.901 (0.828–0.974); FE_IP, 0.757 (0.607–0.907), and FE_UA, 0.762 (0.653–0.872). The AUCs of β2M and α1M were not significantly different, whereas those of the other three markers were smaller. The optimal cutoff values with 100 % sensitivity were 1,123 μg/gCr (β2M, specificity 89 %), 15.4 mg/gCr (α1M, specificity 87 %), 3.58 U/gCr (NAG, specificity 46 %), 1.02 % (FE_IP, specificity 0 %), and 3.92 % (FE_UA, specificity 12 %). Urinary β2M and α1M are potentially suitable screening tools for tenofovir-induced KTD. Monitoring either urinary β2M or α1M should be useful in early detection of tenofovir nephrotoxicity.