Poster Presentation Indian Ocean Rim Laboratory Haematology Congress 2019

Determination of reference intervals (RI) for prothrombin time (PT) and activated thromboplastin time (aPTT) at two laboratories using plasma samples from a single cohort. (#81)

Fatmawati Kamal 1 , Halimatun Radziah Othman 1
  1. Universiti Teknologi MARA, Sungai Buloh, Selangor, Malaysia

Introduction: Establishing reference intervals (RI) for routine coagulation tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), with each new reagent lot is recommended by the US Clinical and Laboratory Improvement Amendments (CLIA) legislation and the Malaysian Ministry of Health for the pathology services. The Faculty of Medicine UiTM has two diagnostic laboratories, located at Sungai Buloh and Selayang campuses. We have to use the same samples when establishing the RI at these sites. We decided to test whether freezing and thawing will give a different PT and aPTT results from fresh samples.

Materials and methods: Plasma samples from 60 eligible blood donors were evenly divided into secondary tubes labelled as fresh or thawed. All samples were duplicated to be run in either Sungai Buloh (SBC) or Selayang (SLC) campuses. PT and APTT were immediately performed on all samples labelled as fresh at both campuses using mechanical clot detection coagulation analyser (Stago Diagnostica France). Thawed-labelled samples were stored frozen at -30oC and PT and APTT were performed after thawing. Paired-samples t-test was used to evaluate the impact of freezing and thawing on PT and aPTT at both campuses.

Results and discussion: The mean PT and aPTT of fresh SBC and SLC samples were found to be statistically different, whereas, no significant difference was found in PT and aPTT of thawed samples at SBC and SLC, p>0.05. The mean differences between thawed PT and aPTT in SBC and SLC were 0.071s and 0.2s, respectively. This experiment showed that by freezing, the samples were more stable, and gave more consistent results.

Conclusions: A lot of factors need to be controlled when running the same normal samples at two different sites. Thus, thawed normal samples can be an option in this situation.

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