Reference intervals for prothrombin time and activated partial thromboplastin time derived from Black African Blood Donors at a University Teaching Hospital in Nairobi, Kenya

Abstract

Background: Prothrombin time (PT) and activated partial thromboplastin time (APTT) are important coagulation  screening tests that give an insight into how well the extrinsic and intrinsic arms of the coagulation cascade are  performing. For correct interpretation of laboratory results and avoidance of errors and misdiagnosis, population  specific RIs are most appropriate.

Objectives: This study aimed to establish reference intervals (RIs) for both PT and APTT at the Aga Khan University  Hospital, Nairobi (AKUH-N) laboratory using black African blood donors.

Methods: As per clinical and laboratory standards institute (CLSI) guidelines, at least 120 male and 120 female black  African donors were recruited, and samples collected for PT and APTT, after informed consent. Data on age, gender,  blood group, PT and APTT results were entered into Microsoft Excel® spread sheet for analysis.

Results: A total of 258 study participants were enlisted. The PT reference intervals were 10.50–13.30 seconds while the  APTT reference intervals were 24.13-35.10. Based on reference change value (RCV), both were significantly higher than manufacturer provided intervals. There was a statistically significant lower PT and APTT in females as compared to  males (U=3971 p<0.0005; U=5924.5 p 0.004), while blood group O participants had a significantly higher APTT compared  to non-O participants (U=5613 p 0.004). Our study also found a weak negative correlation of PT with age (Pearson  coefficient -0.127, p 0.049).

Conclusion: We propose that our laboratory adopt a reference interval for PT and APTT for black African individuals that  differs significantly from manufacturer RIs.