Acute renal failure: acute interstitial nephritis: urinary eosinophils helped to diagnose.

Clinical bottom line (level 4)

  1. In patients who had their urine examined for eosinophils, nearly 5% will have acute interstitial nephritis.
  2. Patients with >1% urinary eosinophils were more likely to have acute interstitial nephritis (LR+9.1) .
  3. A negative test made it less likely (LR+0.40) .
  4. Hansel's stain was not clearly more useful than Wright's stain.
Corwin et al: Archives of Pathology Laboratory Medicine 1989; 113: 1256-1258
Expires July 2003

The study

Setting: department of nephrology, university hospital, USA

183 patients (aged ?, ?% male) urine examined for eosinophils in the investigation of renal disease

?independent blinded reference standard, applied in all patients from a consecutive inappropriate spectrum.
Reference standard:
  • acute interstitial nephritis defined with clinical criteria (co-existence of rash, fever, peripheral eosinophilia, onset of renal insufficiency coincident with often incriminated drug); renal biopsy (the proportion of patients who underwent biopsy was not reported)
Diagnostic test: urine for eosinophils by Hansel's stain and Wright's stain. White blood cells were examined in centrifuged urine, 100 to 150 cells were counted and >1% eosinophils was accounted a positive test. Patients with insufficient white cells to permit determination of percentage eosinophils are included as negative.
  • The presenting clinical syndromes were urinary tract infection (20%), acute tubular necrosis (16%), prerenal azotaemia (22%), diabetic nephropathy (9%) and chronic renal failure (11%).

The evidence

pre-test probability of acute interstitial nephritis: 4.4%, (95% CI: 1.4% to 7.3%)

diagnostic test acute interstitial nephritis no acute interstitial nephritis LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
Hansel's stain 5 12 9.1
(4.2 to 20) 		29% 0.40
(0.16 to 0.99) 		2%
Wright's stain 2 7 6.3
(1.5 to 25) 		22% 0.78
(0.52 to 1.2) 		3%
total 8 175

Comments

  1. Patients had urinary eosinophils determined for clinical reasons and the finding of eosinophiluria may have influenced decisions to proceed to renal biopsy, or the final diagnosis on clinical grounds- incorporation bias may be a significant problem here.
  2. Only large multicenter study of AIN, using kidney biopsy in each case as standard of diagnosis, can truly establish the real predictive value of eosinophiluria as a diagnostic test. Such study, though desirable, is unlikely to happen any time soon.
  3. False positive urinary eosinophils were noted in urinary tract infection (3), acute tubular necrosis (1) and glomerulonephritis (1).

Citation

  1. Corwin HL, Bray RA, Haber MH: The detection and interpretation of urinary eosinophils. Archives of Pathology Laboratory Medicine 1989; 113: 1256-1258
Search Terms: reference list
Contributor: Catherine Clase, Chris Ball and Clare Wotton, April 2000
Reviewer: Mohammad Saklayen

Clinical Question.
Patient urine examined for eosinophils
Intervention or Exposure Hansel's and Wright's stain
Comparison clinical criteria
Outcome diagnosis of acute interstitial nephritis