TDF Group Research Articles

Subclinical Tubular Injury in HIV-Infected Individuals on Antiretroviral Therapy: A Cross-sectional Analysis

Randomized control studies have not shown an association between treatment with tenofovir (TDF) and clinically significant kidney toxicity. However, multiple cases of renal tubular toxicity have been described in patients with HIV treated with TDF. It is unclear whether spot urine protein- or albumin-creatinine ratio is a sufficiently sensitive screening test to detect subclinical renal tubular toxicity in patients with HIV. Cross-sectional. 99 patients with HIV with serum creatinine levels < 1.70 mg/dL and dipstick-negative proteinuria; 19 were antiretroviral treatment (ART) naive, 47 were on a TDF regimen, and 33 were on ART, but with no history of TDF exposure. Exposure to TDF. Spot urine concentrations of retinol-binding protein (RBP; a low-molecular-weight protein normally reabsorbed by the proximal tubule), N-acetyl-beta-D-glucosaminidase (NAG; a proximal tubule lysosomal enzyme), albumin (A; a marker of glomerular disease), and protein (P; a standard clinical screening test for kidney pathological states) expressed as a ratio to creatinine (C; U(RBP/C), U(NAG/C), U(A/C), and U(P/C), respectively). There were no significant differences in median U(A/C) (ART-naive, 7.3 mg/g [range, 0-245.8 mg/g]; TDF, 9.0 mg/g [range, 0.1-184.1 mg/g]; and non-TDF, 10.5 mg/g [range, 2.6-261.6 mg/g]; P = 0.8). U(RBP/C) excretion was significantly higher in the TDF group (median, 214.2 microg/g [range, 26.8-17,454.5 microg/g]) than in the ART-naive group (92.5 microg/g [range, 21.3-3,969.0 microg/g]; P = 0.03); there was also a trend toward higher values than in the non-TDF group (111.6 microg/g [range, 31.0-6,136.3 microg/g]; P = 0.08). U(NAG/C) excretion was significantly higher in both the TDF (median, 394.7 micromol/h/g [range, 140.5-10,851.3 micromol/h/g]; P = 0.01) and non-TDF (406.8 micromol/h/g [range, 12.4-8,485.8 micromol/h/g]; P = 0.03) groups compared with the ART-naive group (218.6 micromol/h/g [range, 56.5-2,876.1 micromol/h/g]). U(P/C) was significantly higher in the TDF (median, 123.9 mg/g [range, 53.1-566.4 mg/g]) than the non-TDF group (97.3 mg/g [range, 0-451.3 mg/g]; P = 0.03). The proportion of patients with evidence of tubular dysfunction (increased U(RBP/C) and/or U(NAG/C)) was considerably higher than the proportion with an increase in U(A/C) or U(P/C) in all groups: for ART-naive, 52.6% vs 31.6% vs 25.0%; for TDF, 80.9% vs 29.8% vs 52.2%; and for non-TDF, 81.8% vs 39.4% vs 30.0%. The level of agreement among the different urinary test results was low. Causality cannot be established from single measurements of urinary markers in a cross-sectional study. Patients with HIV had high rates of subclinical proteinuria, but neither U(P/C) nor U(A/C) is sufficiently sensitive alone to detect many of these cases. Patients using TDF have increased U(RBP/C) and U(P/C); the significance of this will need to be determined from longer-term outcome studies.

Comparison of the antiviral activity of adefovir and tenofovir on hepatitis B virus in HIV–HBV-coinfected patients

Characteristics and factors influencing viral decay under tenofovir (TDF) and adefovir (ADV) need to be determined in HIV-HBV-coinfected patients. This open-label study compared the HBV dynamics in 85 HIV-HBV-coinfected patients initiating an antiretroviral regimen, either including TDF or associated with ADV. The first 6-month change in viral load was analysed using mixed linear models. The adjusted hazards ratio, comparing the rates of undetectable HBV DNA between treatments, was calculated using a Cox proportional hazard model. The HBV DNA decay, adjusted for baseline HBV viral load was more pronounced in patients treated with TDF than with ADV at 12 months (66% versus 53%, P=0.0001). Patients in the TDF group presented a steeper slope of decline at 1.1 (95% confidence interval [CI] 0.9-1.3), compared with 0.8 (95% CI 0.6-1.0) in the ADV group (P=0.036). The mean time to HBV DNA undetectability was 19.3 months (95% CI 16.7-22.0) with TDF and 25.9 months (95% CI 21.1-30.7) with ADV. When adjusted for hepatitis B virus e antigen, HBV DNA and alanine aminotransferase levels at baseline, the influence of treatment on time to HBV DNA undetectability remained in favour of TDF versus ADV (hazard ratio=2.79, 95% CI 1.05-7.40, P=0.039) TDF influenced more strongly the early-phase HBV DNA kinetics than ADV. This is associated with a sustained antiviral activity in the TDF group, in which patients reached the threshold of HBV undetectability at a faster rate and in a larger proportion than those taking ADV.

Low Frequency of Renal Function Impairment During One-Year of Therapy with Tenofovir-Containing Regimens in the Real-World: A Case-Control Study

Concern exists about the risk of nephrotoxicity using tenofovir (TDF) in HIV-infected patients. We performed a retrospective case-control study including 122 consecutive TDF-naive patients who started treatment with TDF-containing regimens and 194 patients receiving antiretroviral therapy with other antiretroviral drugs. During a 12-month observation period 5 (4.1%) patients in the TDF group versus 1 (0.5%) in the control group developed grade 1 or higher serum creatinine elevations (p = 0.018). Only 2 (1.6%) patients discontinued TDF treatment as a result of serum creatinine level elevations. In 4 of the 5 patients developing creatinine elevations TDF was combined with lopinavir-ritonavir. The use of TDF in clinical practice during a 12-month period is associated with low risk of mild renal failure. Further studies to assess long-term renal safety of this drug are needed.

Validation of the PAC-SYM questionnaire for opioid-induced constipation in patients with chronic low back pain

Background The Patient Assessment of Constipation Symptoms (PAC-SYM) questionnaire is a 12-item self-report instrument divided into abdominal, rectal and stool domains. Aims This study aimed to (1) evaluate the psychometric properties of PAC-SYM in assessing the symptoms and severity of opioid-induced constipation; (2) test for differences in opioid-induced constipation between Durogesic ® fentanyl transdermal reservoir (TDF) and oral sustained-release morphine (SRM) in patients with chronic low back pain (CLBP). Methods In a 13-month, open-label, parallel-group study, 680 patients were randomised to receive either TDF ( n = 338) or SRM ( n = 342) for CLBP. Assessments were recorded at Visit 1 (baseline), Visit 5 (Day 29) and Visit 17 (Month 13). Concurrent validity, clinical validity and responsiveness of PAC-SYM were determined based on patients’ confirmation of constipation (CC) scores. Differences in PAC-SYM scores between treatment groups were also evaluated. Results The study included 677 patients, of whom 638 were opioid-naı¨ve. Mean PAC-SYM scores for constipated patients were substantially higher than for non-constipated patients, demonstrating good clinical validity for PAC-SYM. The PAC-SYM could detect changes in bowel function over the treatment period, indicating responsiveness. Homogeneity of each symptom domain exceeded Cronbach’s α coefficient of 0.70, suggesting good internal consistency and reliability. Changes in mean PAC-SYM scores from baseline to Visit 5 and Visit 17 were significantly lower for the TDF group than for the SRM group, indicating that the TDF group experienced less severe constipation. Conclusion PAC-SYM is a reliable, valid and responsive measure of the presence and severity of opioid-induced constipation symptoms.