title: Effects of environmental conditions on point-of-care cardiac biomarker test performance during a simulated rescue: implications for emergency and disaster response.
abstract: OBJECTIVE
  To characterize the effects of environmental stress on point-of-care (POC) cardiac biomarker testing during a simulated rescue.
  
  
  METHODS
  Multiplex test cassettes for cardiac troponin I (cTnI), brain natriuretic peptide (BNP), CK-MB, myoglobin, and D-dimer were exposed to environmental stresses simulating a 24-hour rescue from Hawaii to the Marshall Islands and back. We used Tenney environmental chambers (T2RC and BTRC) to simulate flight conditions (20°C, 10 percent relative humidity) and ground conditions (22.3-33.9°C, 73-77 percent). We obtained paired measurements using stressed versus control (room temperature) cassettes at seven time points (T1-7 with T1,2,6,7 during flight and T3-5 on ground). We analyzed paired differences (stressed minus control) with Wilcoxon signed rank test. We assessed the impact on decision-making at clinical thresholds.
  
  
  RESULTS
  cTnI results from stressed test cassettes (n = 10) at T4 (p < 0.05), T5 (p < 0.01), and T7 (p < 0.05) differed significantly from control, when testing samples with median cTnI concentration of 90 ng/L. During the ground rescue, 36.7 percent (11/30) of cTnI measurements from stressed cassettes generated significantly lowered results. At T5, 20 percent (2/10) of cTnI results were highly discrepant-stressed cassettes reported normal results, when control results were >100 ng/L. With sample median concentration of 108 pg/mL, BNP results from stressed test cassettes differed significantly from controls (p < 0.05).
  
  
  CONCLUSIONS
  Despite modest, short-term temperature elevation, environmental stresses led to erroneous results. False negative cTnI and BNP results potentially could miss acute myocardial infarction and congestive heart failure, confounded treatment, and increased mortality and morbidity. Therefore, rescuers should protect POC reagents from temperature extremes.
authors.affiliation: Assistant Professor, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Louie
authors.affiliation: Staff Research Associate, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: William J
authors.initials: WJ
authors.lastname: Ferguson
authors.affiliation: Research Specialist, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: Corbin M
authors.initials: CM
authors.lastname: Curtis
authors.affiliation: Research Specialist, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: John H
authors.initials: JH
authors.lastname: Vy
authors.affiliation: Research Assistant, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: Chloe S
authors.initials: CS
authors.lastname: Tang
authors.affiliation: Professor, UC Davis POC Technologies Center, Point-of-Care Testing Center for Teaching and Research (POCT • CTR), Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, California.
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Kost
mesh_terms: D015415:Biomarkers; D001774:Blood Chemical Analysis; D052279:Creatine Kinase, MB Form; D004632:Emergency Medical Services; D004777:Environment; D005338:Fibrin Fibrinogen Degradation Products; D006334:Heart Function Tests; D006801:Humans; D009211:Myoglobin; D020097:Natriuretic Peptide, Brain; D019095:Point-of-Care Systems; D018635:Rescue Work; D013312:Stress, Physiological; D019210:Troponin I
chemical_list: D015415:Biomarkers; D005338:Fibrin Fibrinogen Degradation Products; D009211:Myoglobin; D019210:Troponin I; C036309:fibrin fragment D; D020097:Natriuretic Peptide, Brain; D052279:Creatine Kinase, MB Form