title: Zinc protoporphyrin levels have added value in the prediction of low hemoglobin deferral in whole blood donors.
abstract: BACKGROUND
  Increased zinc protoporphyrin (ZPP) levels can indicate iron deficiency and may be predictive for low hemoglobin (Hb) deferral in blood donors. Prediction models for Hb deferral in whole blood donors have already been developed. In this study, we examined if addition of ZPP to these prediction models improves risk estimation of Hb deferral.
  
  
  METHODS
  This study included 4598 Dutch whole blood donors. Information on ZPP levels measured at the previous visit was added to the existing prediction models to estimate the risk of Hb deferral. Models were compared using the following measures: concordance (c)-statistic, continuous net reclassification improvement (NRI), and clinical net benefit (NB).
  
  
  RESULTS
  Seventy-six male donors (2.9%) and 69 female donors (3.5%) were deferred because of a low Hb level. Previous ZPP level was associated with risk of Hb deferral (odds ratio for interquartile range of previous ZPP level, men 2.0 [95% confidence interval {CI}, 1.7-2.3]; women 2.2 [95% CI, 1.9-2.4]) in a multivariable risk model. Addition of ZPP into the models resulted in an increase of the c-statistic from 0.93 to 0.94 for men and from 0.80 to 0.85 for women. The added value of ZPP was confirmed by measures of clinical usefulness. NRI for men was 0.42, and for women, 0.56. At relevant threshold probabilities between 10 and 15%, NB was higher for models considering ZPP.
  
  
  CONCLUSIONS
  This study shows that ZPP measurements obtained at the previous visit may have added value in the risk prediction of Hb deferral in whole blood donors.
authors.affiliation: Department of Donor Studies, Sanquin Research, The Netherlands. m.baart@sanquin.nl
authors.forename: A Mireille
authors.initials: AM
authors.lastname: Baart
authors.forename: Wim L A M
authors.initials: WL
authors.lastname: de Kort
authors.forename: Karel G M
authors.initials: KG
authors.lastname: Moons
authors.forename: Femke
authors.initials: F
authors.lastname: Atsma
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Vergouwe
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001782:Blood Donors; D015331:Cohort Studies; D003661:Decision Support Techniques; D046148:Donor Selection / Q000379:methods*; D005260:Female; D006454:Hemoglobins / Q000172:deficiency* / Q000378:metabolism; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011524:Protoporphyrins / Q000097:blood*; D018570:Risk Assessment
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D011524:Protoporphyrins; C017803:zinc protoporphyrin