title: Age, sex, and racial influences on the Beckman Coulter AccuTnI+3 99th percentile.
abstract: BACKGROUND
  Beckman Coulter recently released a new cardiac troponin I (cTnI) assay, AccuTnI+3, for the Access 2 and DxI platforms. We validated the stated 99th percentile (20 ng/l) using a large population of healthy adults representative of the Northern California population.
  
  
  METHODS
  Within a large sample of healthy adult members receiving care at Kaiser Permanente, cTnI was quantified in residual specimens using the AccuTnI+3 assay. Patients were selected based on pre-defined criteria extracted from a comprehensive electronic medical record. All specimens with a cTnI concentration >30ng/l were repeated; specimens that had a reproducible result >30 ng/l were subject to heterophile blocking procedure. 99th percentiles were calculated based on age, sex, race and body mass index categories.
  
  
  RESULTS
  Among 1764 tested subjects, the 99th percentile for all samples was 25 ng/l. Sex differences were observed; the male and female 99th percentiles were 31 and 21 ng/l, respectively (p=0.001). Age (range evaluated 18-89y, median 47y) also had a significant influence on the value (p=0.003), but there were no significant differences by race. False positive results were detected in 0.9% of specimens (0.6% "fliers" and 0.3% heterophile antibodies), corresponding to 52% of all results >30 ng/l.
  
  
  CONCLUSIONS
  Among a large, representative cohort of healthy adults, we found a 99th percentile value consistent with prior studies based on highly selected small patient samples. Sex and age-specific upper reference limits for cTnI should be considered. In this cohort, about half the findings above the 99th percentile were false positives. Avoiding reporting erroneous results requires implementation of quality indicators.
authors: Kaiser Permanente, TPMG Northern California Regional Laboratory, Berkeley, CA, United States. Electronic address: dngreene@uw.edu.
authors: Dina N
authors: DN
authors: Greene
authors: Division of Research, Kaiser Permanente Northern California, Oakland, CA, United States.
authors: Thomas K
authors: TK
authors: Leong
authors: Clinical Blood Sciences, St Georges Hospital and Medical School, London, UK; Cardiology, St George's Hospital and Medical School, London, UK.
authors: Paul O
authors: PO
authors: Collinson
authors: Kaiser Permanente, TPMG Northern California Regional Laboratory, Berkeley, CA, United States.
authors: Sandy M
authors: SM
authors: Kamer
authors: Kaiser Permanente, TPMG Northern California Regional Laboratory, Berkeley, CA, United States.
authors: Karl
authors: K
authors: Huang
authors: Kaiser Permanente, TPMG Northern California Regional Laboratory, Berkeley, CA, United States.
authors: Thomas S
authors: TS
authors: Lorey
authors: Division of Research, Kaiser Permanente Northern California, Oakland, CA, United States; Departments of Epidemiology, Biostatistics and Medicine, University of California, San Francisco, San Francisco, CA, United States; Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, United States.
authors: Alan S
authors: AS
authors: Go
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001681:Biological Assay; D019411:Clinical Laboratory Techniques; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D044469:Racial Groups; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D019210:Troponin I / Q000097:blood*; D055815:Young Adult
chemical_list: D019210:Troponin I
keywords: 99th percentile; AccuTnI+3; Beckman Access; False positive; Troponin; cTnI