Urinary Beta 2 Microglobulin and Nonsteroidal Anti-inflammatory Drugs

A BSTRACT Background: Urinary beta 2 microglobulin levels (UB2) are indicative of tubular proteinuria and suggest tubular inflammation. This exploratory study was done to determine UB2 levels after ingestion of Nonsteroidal anti-inflammatory drugs (NSAIDs) and to explore their association with reduced glomerular filtration rate (GFR) that could indicate asymptomatic acute tubulointerstitial nephritis. Methods: Urine samples were collected for a routine examination and UB2 levels from one to five days after the NSAID dose ingestion, which was given in the appropriate dose in a Pediatric outpatient department and demographic, dose data were collected. If the UB2 level was elevated (more than 300 ng/mL), the child underwent a blood test to measure the serum creatinine, and the estimated GFR (eGFR) was calculated based on the modified Schwartz formula. Results: Of 50 children in the study (22 girls and 28 boys), 33 children had received Ibuprofen, and 17 children had received mefenamic acid in appropriate doses from 1 to 6 times. Thirty-four children had received NSAIDs for fever, 14 children for pain, and 2 for fever and pain. In 20 children, UB2 was elevated (14/33 children ibuprofen, 6/17 children mefenamic acid). Of these, 12 showed a reduced eGFR, and 5/12 children showed a severely reduced eGFR (<60 mL/min). One child underwent a kidney biopsy that showed Acute tubulointerstitial nephritis (TIN). In the other children, eGFR improved without intervention. Conclusion: In this study, we demonstrated that UB2 levels were elevated after ingestion of NSAIDs in a significant proportion of children. Reduced GFR was seen in 60% of these children. Larger studies are required to conclusively prove the association of NSAIDs with elevated UB levels.