title: Precision, accuracy, and reliability of hemoglobin assessment with use of capillary blood.
abstract: BACKGROUND
  Previous research has suggested that there may be significant within-subject variability, both site-to-site and over time, in hemoglobin concentrations in capillary blood.
  
  
  OBJECTIVE
  This study examined the reliability of the portable hemoglobinometer (PHM) system with use of capillary blood and the implications of errors of the magnitude found for the classification of anemia status in individuals and population groups. The precision and accuracy of the method with use of venous blood were also tested.
  
  
  METHODS
  Three empirical data sets were used to measure reliability, precision, and accuracy of the PHM system [2 from Honduras (n = 87 and 141); 1 from Bangladesh (n = 73)]. Simulation data were used to assess the implications of errors for screening individuals for anemia and to estimate anemia prevalence.
  
  
  RESULTS
  High within-subject variability (unreliability) was identified when capillary blood from the left hand was compared with that from the right hand (CV: 6.3%) and when measurements were taken on 4 consecutive days (CV: 7.0%). Reliability was only 69% and 50%, respectively. Precision and accuracy, however, were very high (concordance coefficients of 0.99 and 0.98 and CV < 1%).
  
  
  CONCLUSIONS
  The simulation data showed that errors of the magnitude found due to unreliability can lead to misclassification of anemia status in individuals and small biases in anemia prevalence estimates. We recommend replicate sampling to reduce the influence of unreliability in the use of the PHM system with capillary blood.
authors.affiliation: Food Consumption and Nutrition Division, International Food Policy Research Institute, Washington, DC 20006-1002, USA. s.morris@cgiar.org
authors.forename: S S
authors.initials: SS
authors.lastname: Morris
authors.forename: M T
authors.initials: MT
authors.lastname: Ruel
authors.forename: R J
authors.initials: RJ
authors.lastname: Cohen
authors.forename: K G
authors.initials: KG
authors.lastname: Dewey
authors.forename: B
authors.initials: B
authors.lastname: de la Brière
authors.forename: M N
authors.initials: MN
authors.lastname: Hassan
mesh_terms: D000293:Adolescent; D000328:Adult; D000740:Anemia / Q000097:blood / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D001459:Bangladesh / Q000453:epidemiology; D015982:Bias; D001774:Blood Chemical Analysis; D002196:Capillaries; D002648:Child; D004868:Equipment Failure; D005260:Female; D006452:Hemoglobinometry / Q000295:instrumentation; D006454:Hemoglobins / Q000032:analysis*; D006721:Honduras / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results
chemical_list: D006454:Hemoglobins