title: Reproducibility of Manual Platelet Estimation Following Automated Low Platelet Counts.
abstract: OBJECTIVE
  Manual platelet estimation is one of the methods used when automated platelet estimates are very low. However, the reproducibility of manual platelet estimation has not been adequately studied. We sought to assess the reproducibility of manual platelet estimation following automated low platelet counts and to evaluate the impact of the level of experience of the person counting on the reproducibility of manual platelet estimates.
  
  
  METHODS
  In this cross-sectional study, peripheral blood films of patients with platelet counts less than 100 × 109/L were retrieved and given to four raters to perform manual platelet estimation independently using a predefined method (average of platelet counts in 10 fields using 100× objective multiplied by 20). Data were analyzed using intraclass correlation coefficient (ICC) as a method of reproducibility assessment.
  
  
  RESULTS
  The ICC across the four raters was 0.840, indicating excellent agreement. The median difference of the two most experienced raters was 0 (range: -64 to 78). The level of platelet estimate by the least-experienced rater predicted the disagreement (p =0.037). When assessing the difference between pairs of raters, there was no significant difference in the ICC (p =0.420).
  
  
  CONCLUSIONS
  The agreement between different raters using manual platelet estimation was excellent. Further confirmation is necessary, with a prospective study using a gold standard method of platelet counts.
authors.affiliation: Oman Medical Specialty Board, Muscat, Oman.
authors.forename: Zainab S
authors.initials: ZS
authors.lastname: Al-Hosni
authors.affiliation: Department of Hematology, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Murtadha
authors.initials: M
authors.lastname: Al-Khabori
authors.affiliation: Department of Hematology, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Sahimah
authors.initials: S
authors.lastname: Al-Mamari
authors.affiliation: Department of Hematology, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Jamal
authors.initials: J
authors.lastname: Al-Qasabi
authors.affiliation: Department of Hematology, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Hiedi
authors.initials: H
authors.lastname: Davis
authors.affiliation: Department of Medicine, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Hatim
authors.initials: H
authors.lastname: Al-Lawati
authors.affiliation: Department of Hematology, Sultan Qaboos University Hospital, Muscat, Oman.
authors.forename: Arwa Z
authors.initials: AZ
authors.lastname: Al-Riyami
keywords: Blood Platelets; Examination; Interpretation; Peripheral Blood Smear; Reliability