Background The summary of product characteristics of tenofovir-disoproxil fumarate (TDF) recommends monitoring renal function periodically, as it has been related to hypophosphatemia and tubulopathy. Evidence links hypophosphatemia in HIV patients with hypovitaminosis D and other antiretrovirals.

However, hypophosphatemia as early marker of renal failure is questionable since bone phosphate reserves could compensate for renal loss.

Purpose To analyse hypophosphatemia as an early marker of renal toxicity in HIV patients treated with antiretroviral therapy (ART) and to study TDF involvement as a cause.

Material and methods Retrospective, observational study including HIV patients receiving ART who had their renal function monitored from 1 January 2013 to 15April 2014.

Results Hypophosphatemia occurred in 18 (17%) of 107 HIV patients monitored for renal function; 16 (89%) males and 2 (11%) females. Mean age was 50 ± 8 years. Hypophosphatemia was classified as isolated if it was not accompanied in any case by possible alterations of tubulopathy. Regarding TDF involvement, 13 (72%) of patients were exposed to the drug when hypophosphatemia was detected.

Follow-up was feasible in 14 patients (78%). ART was modified in 7 (50%), all of them TDF-exposed, with resolution or improvement of the hypophosphatemia in 5 (36%), no change in 1 (7%) and assessment pending in 1 (7%). In the other 7 (50%) cases, 4 TDF-exposed and 3 non-exposed, the treatment was not changed: 3 (21%) due to multidrug resistance, 3 (21%) to hypovitaminosis D and 1 (7%) who was awaiting assessment.

Conclusion The results suggested that hypophosphatemia in HIV patients taking ART might be multifactorial and its use as an early marker of renal toxicity is inconclusive.

To identify the cause of hypophosphatemia in each patient and establish an individualised therapeutic approach, it would be advisable to make a complete baseline study before starting ART.

References and/or acknowledgements No conflict of interest.