Reference Intervals of Prothrombin Time and Activated Partial Thromboplastin Time and Their Association with Age among Healthy Adults in Kumasi, Ghana

Abstract

Prothrombin time (PT) and activated partial thromboplastin time (APTT) are used to assess blood coagulation disorders. Use of reference intervals from a different population may result in misinterpretation and misdiagnoses as the reference intervals for the two tests vary from one geographical area to the other. This study established reference intervals for PT and APTT and evaluated their association with age among healthy adults in Kumasi, Ghana. A total of 876 healthy adults, 18-48 years, all residents of Kumasi, Ashanti region, Ghana were recruited for this cross-sectional study conducted at Komfo Anokye Teaching Hospital (KATH). PT and APTT were determined using the Biobase COA series Semi Auto Coagulation Analyzer following the manufacturer’s instructions. Reference intervals were established using non-parametric approach: 2.5th-97.5th percentiles. The reference intervals for PT and APTT were 11.4-15.9 seconds and 26.3-44.1 seconds respectively. The reference intervals were wider compared to the reference intervals used at KATH. Participants between the ages of 21-30 years old had significantly higher PT and APTT compared with participants between 18-20 years and 31-48 years old. PT was inversely associated with age (β = -1.092, p=.000) among the general population. Upon grouping subjects by gender, PT showed a significant inverse association (β = - .705, p=.000) among males and a direct association (β = .566, p=.004) among females. The association between age and APTT was not statistically significant. There are wider reference intervals for PT and APTT among people in Kumasi. Due to geography, lifestyle, and genetic diversity, it is advisable that each laboratory establishes geography-specific reference intervals for PT and APTT.