Protein and creatine supplements and misdiagnosis of kidney disease

The past five years has seen increasing emphasis on the early detection and treatment of chronic kidney disease, together with reporting of estimated glomerular filtration rate (GFR) alongside serum creatinine values. 1 Most laboratories calculate estimated GFR automatically, using age, serum creatinine, gender, and ethnic group. 2 Increasing reliance on this value as a marker of chronic kidney disease means that any factor which affects creatinine independently of true changes in renal function may lead patients to be misdiagnosed with kidney disease. Also, doctors have become more aware of the importance of reduction of estimated GFR. We report a series of patients referred for investigation of kidney disease (both acute and chronic) in whom ingestion of protein and creatine supplements led to a high serum creatinine and low reported estimated GFR in the absence of kidney disease.

Case reports

A 46 year old white man presented with a two month history of flu-like symptoms and headache and was found to be HIV positive. Routine blood tests showed a serum creatinine of 113 μmol/l (normal <115 μmol/l), giving him an estimated GFR, as calculated by the hospital laboratory, of 64 ml/min/1.73 m² (normal >90 ml/min/1.73 m² ). His CD4 count at the time of diagnosis was 320 cells x10⁶ /l (normal >600 cells x10⁶ /l) with a viral load of 34â[euro][per thousand]344 copies/ml. HIV antiretroviral therapy was started, and one month later at routine review he was found to have a serum creatinine concentration of 166 μmol/l and an estimated GFR of 41 ml/min/1.73 m² . He was referred for a renal opinion, the concern being that he had underlying kidney disease associated with HIV or acute kidney injury induced by antiretroviral drugs.

He had no family history of renal disease, no medical history, and no urinary symptoms. At time of renal review he was taking the antiretroviral agents Kivexa (abacavir and lamivudine), atazanavir, and ritonavir; no other drugs; and occasional non-steroidal anti-inflammatory agents. On examination he weighed 78 kg; blood pressure was normal (122/65 mm Hg); cardiovascular, respiratory, and abdominal examination was unremarkable; and urine dipstick testing was negative for blood, protein, and glucose.

His CD4 count had increased to 449 cells x10⁶ /l and viral load was...