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  10th Intl Workshop on Adverse Drug Reactions and Lipodystrophy in HIV,
London, UK Nov 6-8 2008
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Comparison of Directly Measured and Estimated Glomerular Filtration Rates in Virologically Suppressed Patients Switching to Tenofovir or Continuing Zidovudine
  Reported by Jules Levin
10th Intl Workshop on Adverse Drug Reactions and Lipodystrophy in HIV
London, UK Nov 6-8 2008
SME Vrouenraets 1,2, E Fernandez Garcia2, FWNM Wit1,2, K Brinkman3, FJ Hoek1, RT Krediet1 and P Reiss1,2 for the PREPARE Study Group
1 Academic Medical Center, Amsterdam, the Netherlands;
2 IATEC, Amsterdam, the Netherlands;
3 Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands
Author Conclusions and Interpretations
24 weeks after switching to tenofovir mean measured GFR had decreased by approximately 10%, whereas GFR did not decline in patients who continued on zidovudine
Longer follow-up, which is ongoing, is warranted to determine the course of these changes with continued tenofovir exposure
True GFR in this population with preserved renal function and suppressed HIV-infection was best estimated by the Cockcroft-Gault equation and 24 hour urine calculated creatinine clearance
The MDRD-4-, MDRD-6- and cystatin C-based estimated GFR all tended to underestimate true GFR
Based on our findings, the Cockcroft-Gault equation is likely to be the simplest and most reliable tool for monitoring GFR in HIV-infected individuals in clinical practice and studies
Limitations from Authors
Limited sample size and mainly Caucasian population
Results may be different in a population with more compromised renal function, but no reason to suspect Cockcroft-Gault to not also perform well in such a condition
Could results have been different in patients with ongoing viral replication which is known to potentially adversely affect renal function?


Tenofovir has been associated with nephrotoxicity, including decreased creatinine clearance and proximal tubular dysfunction
All studies used estimated evaluations of creatinine clearance
The accuracy of estimations of glomerular filtration rate (eGFR) however is unknown in HIV-infected patients
To evaluate the effect of initiating a tenofovir-containing regimen on GFR
To compare estimations of GFR with measured GFR by gold-standard approach