title: Rapid visual colorimetry of peritoneal lavage fluid.
abstract: OBJECTIVE
  That visual colorimetry can be used to rapidly and precisely estimate the erythrocyte count of 1:5 dilutions of simulated peritoneal lavage fluid.
  
  
  METHODS
  Fifty-four normal adult human subjects.
  
  
  METHODS
  The automated or chamber RBC count is often used on fluid obtained by peritoneal lavage in patients with abdominal trauma to help determine the need for surgery. Unfortunately, this method sometimes results in excessive delay. We designed and built a simple colorimeter that facilitated rapid direct visual comparison of unknown samples with known color standards. A radiograph view box was used as a light source. Standards were prepared in 16-mm glass tubes to simulate peritoneal lavage fluid with RBC counts ranging from 0 to 140,000 in 10,000 cell/microL increments; 1:5 dilutions with water were used throughout to reduce opacity. Thimerosal was added to unknowns and standards to stabilize color; all samples were kept refrigerated at 4 C when not in use. In a double-blind in-vitro study, each subject matched 20 randomly distributed unknowns ranging from 12,000 to 131,000 erythrocytes/microL to the nearest standard.
  
  
  RESULTS
  The mean absolute error for all 1,080 determinations was 3,560 RBC/microL (95% CI = 4,290-4,830; SD = 4,560; t = 39.6; df = 1,079; P less than .001). This method correctly predicted the RBC count to within 9,000 cells/microL 95% of the time.
  
  
  CONCLUSIONS
  Visual comparison of 1:5 dilutions of simulated peritoneal lavage fluid with known color standards can be used to rapidly and precisely estimate the erythrocyte count.
authors.affiliation: Division of Emergency Medicine, University of New Mexico School of Medicine, Albuquerque 87131.
authors.forename: D
authors.initials: D
authors.lastname: Tandberg
authors.forename: S T
authors.initials: ST
authors.lastname: Reitmeyer
authors.forename: P R
authors.initials: PR
authors.lastname: Cheney
mesh_terms: D000007:Abdominal Injuries / Q000175:diagnosis / Q000601:surgery; D000293:Adolescent; D000328:Adult; D001202:Ascitic Fluid / Q000166:cytology*; D003124:Colorimetry / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D004311:Double-Blind Method; D004906:Erythrocyte Count; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged