Eosinophils Urine
Urine eosinophil counts are sometimes ordered to diagnose acute interstitial nephritis. The clinical utility of this test has never been proven. Urine eosinophils can be increased in a variety of other diseases including cystitis, prostatitis, pyelonephritis, and glomerulonephritis. Renal biopsy remains the gold standard.
The preferred method is to count the number of eosinophils in urinary sediment after staining with Hansel stain, which is a mixture of methylene blue and eosin Y.
A positive result has been defined as greater than 1% eosinophils, but a result of greater than 5% is more specific for acute interstitial nephritis.
Using a cutoff of 1%, sensitivity for acute interstitial nephritis is only 40% and specificity is only 60%.
