10.22376/ijpbs.2019.10.1.p1-12 Volume 11 Issue 4 2020 (October-December) Hematocrit (Hct) measurement using a centrifuge method is a common laboratory testing procedure at primary care units (PCU). This study evaluated the performance of Hct measurement by a centrifuge method in health promotion hospitals (HPH) using two assigned values from expert laboratories and participant consensus. Two processed blood materials were tested for homogeneity and stability and then used to evaluate the performance of Hct measurement by a centrifuge method. All the materials were distributed to 132 participants, including 24 hospitals and 108 HPHs through the Proficiency Testing (PT) Scheme, following ISO/IEC 17043:2010 guidelines. Assigned robust means and standard deviations (SDs) were calculated from three expert laboratories and consensus from all participants using algorithm A according to ISO 13528: 2015. A paired t-test was used to compare robust means between the expert laboratories and participant consensus. The performance of the Hct measurement using a centrifuge method was evaluated using z scores. The Hct in processed blood materials were homogenous and stable for use as PT materials for three weeks. The means of Hct assigned from the expert laboratories were significantly different ( lessThan i greaterThan p lessThan /i greaterThan lessThan 0.05) from those assigned from participant consensus. Over 80% of HPHs had a satisfactory performance with z scores ≤ 2.00 when using both assigned means from the expert laboratories and participant consensus, with the exception of low levels of Hct when using the assigned mean from the expert laboratories. The Hct measurement performance at a low level of Hct, , was significantly lower compared to using participant consensus (Chi-square =134.89, lessThan i greaterThan p lessThan /i greaterThan lessThan 0.001). This study shows significant differences in the performance of Hct measurement by a centrifuge method when using assigned means from expert laboratories and from all participants. Most of the HPHs had a satisfactory performance for Hct measurement by a centrifuge method when using participant consensus. However, half of HPHs require performance improvement where there are questionable and unsatisfactory evaluations when assigned means from expert laboratories are used. Poonnapatch Sakaew, Kunchit Kongros, Phanthira Wongsri, Napaporn Apiratmateekul and Wanvisa Treebuphachatsakul* Performance evaluations, microhematocrit, packed red cell volume, ISO/IEC 17043, whole blood material, external quality assurance. 77-82