title: Diagnostic value of urine microscopy for differential diagnosis of acute kidney injury in hospitalized patients.
abstract: OBJECTIVE
  Urine microscopy is the oldest and one of the most commonly used tests for differential diagnosis of acute kidney injury (AKI), but its performance has not been adequately studied in the setting of AKI.
  
  
  METHODS
  Fresh urine samples were obtained from 267 consecutive patients with AKI, and urinary sediment was examined. The cause of AKI was assessed at two time points: (1) Before urine microscopy diagnosis and (2) after patient discharge or death (final diagnosis). A urinary scoring system also was created on the basis of casts and renal tubular epithelial cells (RTEC) to differentiate acute tubular necrosis (ATN) from prerenal AKI.
  
  
  RESULTS
  The urinary sediment scoring system was highly predictive of the final diagnosis of ATN. In patients with a high pretest probability of ATN (initial diagnosis of ATN), any casts or RTEC (score > or =2) resulted in very high positive predictive value and low negative predictive value for a final diagnosis of ATN. In patients with a low pretest probability of ATN (initial diagnosis of prerenal AKI), lack of casts or RTEC on urinary sediment examination had a sensitivity of 0.73 and specificity of 0.75 for a final diagnosis of prerenal AKI. The negative predictive value of lack of casts or RTEC in patients with low pretest probability of disease was 91%.
  
  
  CONCLUSIONS
  Urine sediment examination is a valuable diagnostic tool for confirming the diagnosis of ATN. A score of > or =2 on an ATN urinary sediment scoring system is an extremely strong predictor of ATN.
authors.affiliation: Section of Nephrology, Yale University School of Medicine, New Haven, CT 06520-8029, USA. mark.perazella@yale.edu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Perazella
authors.forename: Steven G
authors.initials: SG
authors.lastname: Coca
authors.forename: Mehmet
authors.initials: M
authors.lastname: Kanbay
authors.forename: Ursula C
authors.initials: UC
authors.lastname: Brewster
authors.forename: Chirag R
authors.initials: CR
authors.lastname: Parikh
mesh_terms: D000208:Acute Disease; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D004847:Epithelial Cells / Q000473:pathology; D006801:Humans; D007297:Inpatients; D007674:Kidney Diseases / Q000175:diagnosis* / Q000652:urine; D007683:Kidney Tubular Necrosis, Acute / Q000175:diagnosis* / Q000652:urine; D008853:Microscopy; D008859:Microscopy, Polarization; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D016482:Urinalysis / Q000379:methods*; D014556:Urine / Q000166:cytology
references.citation: JAMA. 2003 Feb 12;289(6):747-51
references.pmid: 12585954
references.citation: Am J Kidney Dis. 2006 Nov;48(5):695-705
references.pmid: 17059988
references.citation: Ann Intern Med. 1978 Jul;89(1):47-50
references.pmid: 666184
references.citation: Ren Fail. 1995 Nov;17(6):721-9
references.pmid: 8771245
references.citation: Kidney Int. 2004 Oct;66(4):1613-21
references.pmid: 15458458
references.citation: Am J Kidney Dis. 2005 Dec;46(6):1038-48
references.pmid: 16310569
references.citation: J Am Med Assoc. 1959 Jul 25;170(13):1533-7
references.pmid: 13664557
references.citation: Am J Kidney Dis. 2002 May;39(5):930-6
references.pmid: 11979336
references.citation: Curr Opin Nephrol Hypertens. 1998 Nov;7(6):681-5
references.pmid: 9864665
references.citation: Ann Intern Med. 2008 Jun 3;148(11):810-9
references.pmid: 18519927
references.citation: Crit Care. 2006;10(3):R73
references.pmid: 16696865
references.citation: Kidney Int Suppl. 1998 Feb;64:S15-8
references.pmid: 9475482
references.citation: Ann Intern Med. 2002 Nov 5;137(9):744-52
references.pmid: 12416948
references.citation: N Engl J Med. 1998 Mar 5;338(10):671-5
references.pmid: 9486997
references.citation: Clin Lab Med. 1993 Mar;13(1):13-20
references.pmid: 8462255
references.citation: Lancet. 2005 Jan 29-Feb 4;365(9457):417-30
references.pmid: 15680458
references.citation: Am Fam Physician. 2005 Nov 1;72(9):1739-46
references.pmid: 16300036
references.citation: Antimicrob Agents Chemother. 1979 Oct;16(4):468-74
references.pmid: 518076
references.citation: Clin Sci. 1950;9(4):379-404
references.pmid: 24540020