title: Impact of preanalytical factors on fecal immunochemical tests: need for new strategies in comparison of methods.
abstract: BACKGROUND
  Harmonization of fecal immunochemical tests for hemoglobin (FIT-Hb) is crucial to compare clinical outcomes in screening programs. The lack of reference materials and standard procedures does not allow the use of usual protocols to compare methods. We propose 2 protocols, based on artificial biological samples (ABS), to discriminate preanalytical and analytical variation and investigate clinical performances. The protocols were used to compare 2 FIT systems available on European markets: the OC-Sensor Diana (Eiken, Tokyo, Japan) and HM-JACKarc (Kyowa-Medex, Tokyo, Japan).
  
  
  METHODS
  ABS were obtained adding Hb to Hb-free feces. In the first procedure, 35 ABS were collected for each collection device and analyzed on both systems. In the second, 188 ABS (106 positive and 82 negative) were -collected and tested on the specific systems. Passing-Bablock (PB), Pearson's correlation coefficients (R) and Bland-Altman difference analysis were used to compare data.
  
  
  RESULTS
  PB, R and mean standard errors for Bland-Altman analysis (Diana vs. Arc) results were 0.93x-0.56: R = 0.97 and 19%; and 1.09x + 5.60: R = 0.96 and -18%; for Diana and Arc devices, respectively. No correlations and no difference in positive/negative assessment were observed with the second protocol.
  
  
  CONCLUSIONS
  A good correlation was observed in comparing data generated using collection devices on the 2 systems. Manufacturers have developed different sample collection procedures for feces: therefore, data from different systems cannot easily be compared. Adoption of protocols to discriminate preanalytical and analytical variation would be a significant contribution to harmonization of FIT, facilitating data comparison and information acquisition for sample collection strategy and effect of buffers on systems.
authors.affiliation: Cancer Prevention and Research Institute (ISPO), Florence - Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Rubeca
authors.forename: Filippo
authors.initials: F
authors.lastname: Cellai
authors.forename: Massimo
authors.initials: M
authors.lastname: Confortini
authors.forename: Callum G
authors.initials: CG
authors.lastname: Fraser
authors.forename: Stefano
authors.initials: S
authors.lastname: Rapi
mesh_terms: D002021:Buffers; D002138:Calibration; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000517:prevention & control*; D055088:Early Detection of Cancer / Q000379:methods* / Q000592:standards; D006452:Hemoglobinometry / Q000379:methods* / Q000592:standards; D006801:Humans; D007120:Immunochemistry; D007202:Indicators and Reagents; D009780:Occult Blood; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods / Q000592:standards
chemical_list: D002021:Buffers; D007202:Indicators and Reagents; D011933:Reagent Kits, Diagnostic