Long-term treatment with tenofovir: prevalence of kidney tubular dysfunction and its association with tenofovir plasma concentration.

BACKGROUND: Monitoring of side effects of long-term HIV treatment has become increasingly important. Tenofovir disoproxil fumarate (TDF), a first-line treatment option, is associated with kidney tubular dysfunction (KTD). Our objective was to further investigate the prevalence and risk factors of KTD, in particular its association with TDF plasma concentration in HIV-infected patients treated with TDF for at least one year. METHODS: An observational cross-sectional single-centre study was conducted. KTD was defined as the presence of at least two of the following criteria: urinary α1-microglobulin/creatinine ratio >15 mg/10 mmol; fractional excretion (FE) of phosphate >20% in the presence of hypophosphataemia; FE of uric acid >10% in the presence of hypouricaemia and glucosuria. Multivariate logistic regression was used to study which variable was associated with KTD. RESULTS: A total of 161 HIV patients were included. Abnormalities in tubular function were observed in 101 patients (62.7%), while 17 patients (10.6%) fulfilled the definition of KTD. Urinary α1-microglobulin/creatinine ratio was the most sensitive parameter to detect KTD. Multivariate logistic regression showed TDF plasma concentration to be the only variable associated with KTD. Post hoc analysis showed a stronger association between the product of TDF plasma concentration and TDF exposure and KTD. CONCLUSIONS: Parameters of KTD are frequently observed in patients on long-term TDF-containing combination antiretroviral therapy. KTD is associated with higher TDF plasma concentrations. A stronger association between the product of TDF plasma concentration and TDF exposure and KTD could suggest cumulative toxicity. A causative role for elevated TDF plasma concentration in development of KTD cannot be demonstrated in this cross-sectional analysis. Longitudinal research is needed to investigate the development and clinical relevance of KTD.

Vitamin D deficiency among HIV type 1-infected individuals in the Netherlands: effects of antiretroviral therapy.

Vitamin D regulates bone metabolism but has also immunoregulatory properties. In HIV-infected patients bone disorders are increasingly observed. Furthermore, low 1,25(OH)(2)D(3) levels have been associated with low CD4(+) counts, immunological hyperactivity, and AIDS progression rates. Few studies have examined the vitamin D status in HIV-infected patients. This study will specifically focus on the effects of antiretroviral agents on vitamin D status. Furthermore, the effect of vitamin D status on CD4 cell recovery after initiation of HAART will be evaluated. Among 252 included patients the prevalence of vitamin D deficiency (<35 nmol/liter from April to September and <25 nmol/liter from October to March) was 29%. Female sex, younger age, dark skin, and NNRTI treatment were significant risk factors in univariate analysis, although in multivariate analyses skin pigmentation remained the only independent risk factor. Median 25(OH)D(3) levels were significantly lower in white NNRTI-treated patients [54.5(27.9-73.8) nmol/liter] compared to white PI-treated patients [77.3 (46.6-100.0) nmol/liter, p = 0.007], while among nonwhites no difference was observed. Both PI- and NNRTI-treated patients had significantly higher blood PTH levels than patients without treatment. Moreover, NNRTI treatment puts patients at risk of elevated PTH levels (>6.5 pmol/liter). Linear regression analysis showed that vitamin D status did not affect CD4 cell recovery after initiation of HAART. In conclusion, 29% of the HIV-1-infected patients had vitamin D deficiency, with skin color as an independent risk factor. NNRTI treatment may add more risk for vitamin D deficiency. Both PI- and NNRTI-treated patients showed higher PTH levels and might therefore be at risk of bone problems. Evaluation of 25(OH)D(3) and PTH levels, especially in NNRTI-treated and dark skinned HIV-1-infected patients, is necessary to detect and treat vitamin D deficiency early.