Recommendation for standardization of haematology reporting units used in the extended blood count M. BRERETON*, R. MCCAFFERTY † , K. MARSDEN ‡ , Y. KAWAI § , ¶ , J. ETZELL**, A. ERMENS †† FOR THE INTERNATIONAL COUNCIL FOR STANDARDIZATION IN HAEMATOLOGY *Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK † St James’s Hospital, Dublin, Ireland ‡ Royal Hobart Hospital, Hobart, Tas., Australia § International University of Health & Welfare, Sanno Affiliate Hospital, Tokyo, Japan ¶ Japanese Society for Laboratory Haematology, Tokyo, Japan **Sutter Health Shared Laboratory, Livermore, CA, USA †† Amphia hospital, Breda, The Netherlands Correspondence: Richard McCafferty, Haematol- ogy Dept., St James’s Hospital, Dublin, Ireland. Tel.: +353 1 4162067; Fax: +353 1 4162920; E-mails: mccaffertyr@eircom.net; Richard.McCafferty@stjames.ie doi:10.1111/ijlh.12563 Received 10 December 2015; accepted for publication 11 July 2016 Keywords ICSH, recommendation, standardization, reporting units, blood count SUMMARY Introduction: It is desirable in the interest of patient safety that the reporting of laboratory results should be standardized where no valid reason for diversity exists. This study considers the reporting units used for the extended blood cell count and makes a new ICSH recommendation to encourage standardization worldwide. Methods: This work is based on a literature review that included the original ICSH recommendations and on data gathered from an interna- tional survey of current practice completed by 18 countries worldwide. Results: The survey results show that significant diversity in the use of reporting units for the blood count exists worldwide. The use of either non-SI or other units not recommended by the ICSH in the early 1980s has persisted despite the guidance from that time. Conclusion: The diversity in use of reporting units occurs in three areas: the persistence in use of non-SI units for RBC, WBC and pla- telet counts, the use of three different units for haemoglobin con- centration and the manual reporting of WBC differential, reticulocytes and nucleated RBCs when the latter are available from automated analysis or can be expressed as absolute numbers by calculation. A new recommendation with a rationale for each parameter is made for standardization of the reporting units used for the extended blood count. 472 © 2016 John Wiley & Sons Ltd, Int. Jnl. Lab. Hem. 2016, 38, 472–482 ORIGINAL ARTICLE INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY International Journal of Laboratory Hematology The Official journal of the International Society for Laboratory Hematology