Markers of Glomerular Filtration Rate in the HIV Infected Patient - Role of Body Composition

Aim of the study :

The aim of our study is to test the different available markers for the estimation of glomerular filtration rate (GFR) in HIV patients in order to determine which one is the more appropriated in this particular population. We will analyze the role of the variation in muscular mass in the estimation of GFR

Background :

Several lines of evidence point to renal disease becoming an important complication of human immunodeficiency virus infection and therapy. The spectrum of renal disease in the HIV patient has dramatically changed with HIV associated nephropathy becoming less prevalent and chronic kidney disease [CKD] becoming an everyday concern parallel to the prevalence of renal risk factors such as aging, hypertension and diabetes. Different studies have shown that the prevalence of CKD defined as an estimated glomerular filtration rate below 60 ml/min/1.73m2 is around 10% in HIV patients. CKD is associated with increased mortality, a new concept that has emerged in the past years putting CKD in the top 5 critical cardiovascular risk factors. Evaluating individual renal function in HIV patients allows better care in prevention of cardiovascular events as well as initiation of nephro-protection strategies in order to slow down the loss of renal function and alleviate or postpone the need for dialysis. Since HIV patients also receive chronic multi-therapy, evaluating renal function is also mandatory to allow drug dosage adaptation.

Plasma creatinine dosage is routinely used to estimate GFR but it is closely correlated to age, sex, weight and ethnic origin of the patients. All these factors make creatinine unreliable for GFR estimation. Laboratory dosage of creatinine may be performed with different techniques (JAFFE or enzymatic dosage) with a 20% variation in the results for the same patient. None of the GFR estimation formulae (Cockcroft et Gault or MDRD) have been validated in HIV patients. Cystatin C, a new marker still under evaluation, seems to show some interest in such patients because of its relative independency with regard to muscle mass, but has not been tested in HIV patients. Some cystatin C based formulae have been proposed but not yet tested and validated in HIV patients. HIV infected patients may exhibit abnormal body composition particularly affecting lipids but also, as shown recently, muscle mass. Our study will precisely measure body composition in order to allow interpretation of the variations of the renal markers with regard to muscle mass.