Chemistry, Microbiology, Test Utilization

Changes in Reflex Criteria for “Urinalysis, do Culture if Indicated” [Update]

On September 1, 2015, Spectrum Health Regional Laboratory, in conjunction with Infectious Disease, Infection Prevention and Pharmacy, adjusted reflex criteria for urine culture based on urinalysis finding (Urinalysis, Do Culture if IndicatedTest #115, Epic #LAB348, UA CX DO IF). The adjustment involved an increase in the number of WBCs per HPF considered positive (from ≥3 to ≥10).

URINE CULTUREs will be performed if 2 of the following 3 criteria are positive:

  • positive leukocyte esterase
  • positive nitrite
  • ≥ 10 WBCs/HPF (previously ≥3 WBCs/HPF)

URINE CULTUREs will not be performed if there are 10 or more squamous epithelial cells per high power field (>10 sq epith/HPF).

A Laboratory/Pharmacy review of one month’s UA CX DO IF requests with WBC between 4 and 9 WBCs/HPF) and at least one other positive criteria (leukocyte esterase and/or positive nitrite) (108 patients selected at random from 833 possible) revealed that no urinary tract infections were missed by raising the WBC cutoff from ≥3 WBCs/HPF to ≥10 WBCs/HPF. In addition, there would have been a 70% drop in the number of urine cultures performed. Furthermore, a number of institutions and commercial laboratories are already using ≥10 WBCs/HPF as their WBC cutoff.

Any questions concerning the change in reflex criteria for urine culture may be directed to Dr. David Alter in the Pathology department.

Burd EM, Kehl KS. A Critical Appraisal of the Role of the Clinical Microbiology Laboratory in the Diagnosis of Urinary Tract Infections. Journal of Clinical Microbiology. 2011;49(9 Suppl):S34-S38. doi:10.1128/JCM.00788-11.

This post was originally made in September 2015 and has been updated with reference information, July 2016.

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