How accurate is creatinine for detecting kidney disease in patients with HIV?
It is now clear that the serum creatinine has significant limitations in many HIV patients as a result of:
1. The dependence of creatinine on gender, age, and underlying nutritional status. Patients with active HIV who are not receiving combination anti-retroviral therapy (cART) may have marked reductions in muscle mass as a result of malnutrition, and will have lower baseline serum creatinine levels than in the general population. It would not be unusual for a patient with advanced, untreated HIV to have a seemingly normal serum creatinine level of 0.9 mg/dL and yet have a significant reduction in eGFR.
2. Interference of HIV therapy with the laboratory measurement of creatinine. Some cART drugs interferes with the tubular secretion of creatinine. Since creatinine is both filtered and secreted, impairment of tubular secretion will increase the serum creatinine even without a change in the GFR. This will cause the eGFR to fall and may lead to an erroneous diagnosis and inappropriate work-up for acute or chronic kidney injury. This process is similar to the spurious elevations of creatinine seen with cimetidine and trimethoprim. Specifically in cART, the integrase strand inhibitors characteristically impede the secretion of creatinine, and it is expected that the creatinine will be higher in these patient by 0.5 mg/dL. Cobicistat, used as a booster for the other cART medications, has also been shown to have the same effect on creatinine secretion. The absence of other markers of kidney injury—that is, abnormal urinary sediment, a normal blood urea nitrogen, and stable clinical course—all support a benign drug-induced elevation of creatinine.
