Urinary beta2-microglobulin as a possible sensitive marker for renal injury caused by tenofovir disoproxil fumarate.

Tenofovir disoproxil fumarate (TDF) is renally excreted by a combination of glomerular filtration and active tubular secretion, and its renal safety profiles have been reported based on a limited increase of serum creatinine (sCr) levels. However, renal tubular function has not previously been well monitored. We measured sCr and urinary beta2-microglobulin (U-beta2MG) levels cross-sectionally in 70 patients treated with TDF [TDF+] and 90 patients on other antiretroviral therapy who had never been exposed to TDF [TDF-]. The mean U-beta2MG was significantly higher in TDF+ patients than that in TDF- patients (p < 0.0001), though no statistical difference was detected in their creatinine clearance estimated by using the Cockcroft-Gault equation. Multivariate analysis showed that coadministration of boosted lopinavir (LPV) and patients' body weight were associated with U-beta 2MG levels in TDF+ patients. U-beta2MG levels were significantly higher in those who also received boosted LPV [TDF+LPV+] (p = 0.0007), and abnormally high levels were noted in 67.7% of them. Furthermore, in the TDF+LPV+ group, U-beta2MG levels showed significant negative correlation with patients' body weight (p = 0.0029) and abnormal U-beta2MG was observed in all six patients with body weight less than 55 kg. In four patients, a rapid fall in U-beta2MG occurred after cessation of TDF. Relative to sCr, U-beta2MG could be a more sensitive marker of renal tubular injury caused by TDF. Boosted LPV co-administration and low body weight may be risk factors for TDF-induced renal tubular dysfunction, probably because these factors are associated with an increase in TDF concentration.