Effect of sodium citrate and magnesium sulphate anticoagulation on platelet parameters measured on the Alinity hq analyzer.

INTRODUCTION: EDTA-dependent pseudothrombocytopenia (PTP) may cause spuriously low platelet counts and can be prevented by using alternative anticoagulants, such as sodium citrate (citrate) and magnesium sulphate (MgSO4). However, these anticoagulants may affect platelet parameters depending on the analytical platform. Their effect on platelet measurements using the Abbott Alinity hq hematology analyzer has not previously been evaluated. METHODS: Blood samples from 40 outpatients without known PTP were collected in K2-EDTA, citrate, and MgSO4 tubes. Platelet count, mean platelet volume, and reticulated platelet fraction were measured on an Alinity hq analyzer. Paired comparisons were performed using Friedman repeated-measures analysis with the Dunn multiple comparisons test. RESULTS: Compared with EDTA, median platelet counts were statistically significantly lower in citrate (-21.1%) and MgSO4 (-31.7%) than in EDTA (P < .05). Mean platelet volume was also statistically significantly reduced in citrate (-3.2%) and MgSO4 (-4.7%) (P < .05). Median reticulated platelet fraction was slightly higher in both anticoagulants, but only MgSO4 differed substantially from EDTA. DISCUSSION: On the Alinity hq analyzer, citrate and MgSO4 result in statistically significantly lower platelet count than EDTA in samples from individuals without known PTP. Platelet parameters are therefore influenced by anticoagulant choice and should not be interpreted interchangeably.