Two and a half months ago I have switched the treatment from Combivir and Sustiva to Truvada and Sustiva (Atripla is still to be approved here). In the test two months after the initiation of the new treatment my urine analysis indicated elevated levels of B-2 Macroglobulin (594 microgram per gram of cr., normal levels given as 0.0 100.0) and N-Acetyl Glucosaminidase (26 crea, normal levels given as 0.2 4.6). I was told that this might indicated Truvada caused renal tubular dysfunction. At this point, my doctor has recommended waiting for 3 months and repeating the tests. We do not have the values before initiating the treatment. Immunological results were good. Other unusual indicators were low chlorine in urine 18 mEq/L (normal 75-200) and sodium 8 mEq/L (75-200). Creatine in urine (16 mg/dL) and creatine blood levels were normal.

At what levels should I start to get concerned with the possible kidney damage? Are these side effects reversible? What are the long-term impacts of the current levels of these proteins? Are there any complications or contra arguments for switching back to Combivir if these problems persist or become worse (the old combination was well tolerated for 4.5 years with a very mild anemia and the switch was initiated based on the long-term mitochondrial toxicity concerns)?

Many thanks!

I haven't seen much looking at urine macroglobulin or N-acetyl glucosaminidase levels and tenofovir related renal toxicity. Monitoring glomerular filtration rate using the Cockcroft-Gault equation has been of some use in monitoring renal function while on tenofovir. Evaluation for possible Fanconi syndrome (< 1 % of patients on tenofovir) often includes serum phosphate level,blood glucose, blood potassium levels and urine glucose and protein. Monitoring urine microalbumin levels is useful for assessing proteinuria particularly in persons at risk for HIV nephropathy or other renal disease (i.e diabetes). If any reader has any references demonstrating the clinical utilility of urine macroglobulin or N-acetyl glucosaminidase levels for diagnosig or monitoring tenofovir nephrotoxicity please post. KH