Evaluating the effectiveness of pseudothrombocytopenia (PTCP) panel with alternative anticoagulants on clinically suspicious EDTA-dependent PTCP: a single tertiary hospital experience

Abstract

Abstract EDTA is considered the most common anticoagulant to induce pseudothrombocytopenia (PTCP). PTCP panel with alternative anticoagulants (heparin and citrate) has been ordered by clinicians in our hospital for suspicious EDTA-dependent PTCP cases to obtain the correct platelet count (PC). In this study, we aimed to evaluate the effectiveness of alternative anticoagulants on clinically suspicious EDTA-PTCP. We retrospectively identified cases for which PTCP panel (EDTA, heparin, and citrate) was performed from June 2021 to March 2022 using the SAP business intelligence tool. PC was considered significantly different when the difference is more than 25% comparing heparin or citrate to EDTA tubes. Representative cases were chosen for chart review and/or peripheral blood smear review. 200 cases were included in the study. 76 cases had similar PCs in all 3 tubes which represent either true thrombocytopenia or PTCP in all 3 tubes. 17 cases had higher PC on heparin and/or citrate than EDTA which are EDTA-PTCP corrected by alternative anticoagulants (confirmed by smear review). Among those 17 cases: 6/17 had high PC on citrate only, 2/17 on heparin only and 9/17 had higher PC on citrate/heparin. 82 cases had lower PC on heparin only compared to EDTA and 62/82 had heparin exposure. There was 1 case with lower PC on citrate only (no heparin tube) compared to EDTA. 24 cases had lower PC in both heparin and citrate than EDTA tubes (lowest PC on Heparin) and 21/24 have heparin exposure. Peripheral blood smears were reviewed in 39 representative cases. Platelet clumps were identified in the corresponding tubes of all cases. Our study shows that heparin-PTCP is common in hospitalized patients and confirms that heparin is not a suitable alternative anticoagulant for EDTA-PTCP as shown by previous literature. However, many laboratories still use it for EDTA-PTCP. Heparin is known to promote platelet activation which may cause PTCP. The low PC in the heparin tube also seems to be associated with prior heparin exposure. Citrate is a better alternative to EDTA-PTCP. Among cases with low PCs on citrate, nearly all have low PCs on heparin as well. It is interesting to note those cases usually have lower PCs on heparin versus citrate and have prior exposure to heparin. The low PCs on citrate might be partially due to insufficient correction (110%) of PC by the dilution factor of the anticoagulant. Literature showed that a higher corrective factor of PCs is required for citrate. Therefore, a correlation study of PCs in EDTA versus citrate in each lab is needed to establish the corrective factor. Furthermore, delayed processing might be contributing as PCs on citrate are less stable and must be processed within 3 hours.