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Risk Factors for for Kidney Disease in EuroSida:
Climbing CD4 Count Cuts Risk of Worsening Kidney Function
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(Poster online at http://www.retroconference.org/2008/PDFs/971.pdf.)
15th Conference on Retroviruses and Opportunistic Infections
February 3-6, 2008
Boston
Mark Mascolini
Rising CD4 counts trimmed the risk of declining renal function by nearly one third in a 5526-person EuroSIDA analysis [1]. An AIDS diagnosis, hepatitis C virus (HCV) infection, and heart disease all inflated the risk of faltering kidneys.
The EuroSIDA group focused on cohort members with (1) at least three serum creatinine measures after January 1, 2004, (2) body weight measured within 12 months of each creatinine reading, and (3) a recorded birth date. Follow-up lasted through autumn 2006. The investigators used both the Cockroft-Gault method and the Modification of Diet in Renal Disease (MDRD) method to estimate glomerular filtration rate (GFR). They defined declining GFR as two consecutive GFRs at or below 60 mL/min/1.73 m(2) after a reading above 60 or a confirmed 25% drop in GFR.
At baseline 227 of the total 5526 patients had a GFR of 60 mL/min or lower at their first measurement. This already-compromised group had a median age of 61 years (interquartile range [IQR] 52 to 69), compared with a median of 43 years (IQR 38 to 51) in the whole study group. Median GFR for the entire group at the first measurement was 95 (IQR 82 to 110), median CD4 count measured 453, and median viral load stood at 50 copies.
Before the first GFR measurement fewer than 5% or fewer cohort members had an acute myocardial infarction (1.4%), carotid endarterectomy (0.1%), coronary artery bypass surgery (0.4%), angioplasty (1.1%), stroke (1.0%), or diabetes (5.3%). But 22.7% had hypertension. Only 7.1% were current smokers and 0.3% past smokers, surprisingly low rates for Europeans. Smoking status was unknown in 20.8%.
After an average of five GFR measures per person, 130 people (2.4%) who averaged more than 60 mL/min on their first two Cockroft-Gault readings fell to 60 or lower on a later reading to yield an incidence of 13.4 cases of renal deterioration per 1000 person-years. Another 175 people (3.2%) had a confirmed 25% drop in GFR from any starting GFR for an incidence of 17.3 per 1000 person-years.
Multivariate analysis (factoring in gender, race, age, prior AIDS, prior use of nephrotoxic drugs, prior heart disease, diabetes, or hypertension, smoking, and other variables) determined that a rising CD4 count during follow-up cut the risk of declining renal function, while several other variables raised the risk:
· Every 2-fold higher latest CD4 count lowered the risk of declining renal function 31% (adjusted relative hazard [AHR] 0.69, 95% confidence interval [CI] 0.55 to 0.87, P = 0.0034).
· Prior AIDS boosted the risk of declining renal function 75% (AHR 1.75, 95% CI 1.10 to 2.79, P = 0.018).
· HCV infection almost tripled the risk (AHR 2.67, 95% CI 1.58 to 4.52, P = 0.0002).
A cardiovascular "event" (defined above), older age, and later year of starting combination antiretroviral therapy also hoisted the risk of faltering kidney function. A higher first GFR and a higher first viral load measurement both lowered the risk. Lowest-ever (nadir) CD4 count had no impact on declining kidney function. The investigators caution that wide confidence intervals surrounded risk estimates for many variables (see poster), so "more exact evaluation of several of these variables requires longer follow-up and more endpoints."
The EuroSIDA team found similar results when they figured GFR by the MDRD method. They did not figure risk by type of antiretroviral regimen or individual drugs but will do so as follow-up continues. The correlation between climbing CD4s and stable renal function suggest an overall kidney benefit for antiretroviral therapy.
Reference
1. Kirk O, Mocroft A, d'Arminio Monforte A, et al. Deterioration of renal function associated with current level of immunodeficiency. 15th Conference on Retroviruses and Opportunistic Infections. February 3-6, 2008. Boston. Abstract 971.
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