Application and Comparison of Direct and Indirect Methods in Establishing Reference Intervals for Coagulation Tests

This study aimed to establish reference intervals for coagulation parameters based on a new coagulation function testing system in our laboratory and to compare the effectiveness of direct and indirect methods. The direct method included patients from the Colorectal Surgery and Dermatology departments, as well as healthy participants from a Phase I drug trial at the West Campus of China-Japan Friendship Hospital, from April to December 2023. Coagulation function data were statistically analyzed by age group to establish reference intervals. The indirect method used refineR to analyze coagulation data from non-ICU patients at the same campus during the same period. To compare the performance of both methods, coagulation data from the Colorectal Surgery and Emergency Department patients, matched with healthy participants, were analyzed. Results showed that the reference intervals for APTT, PT, and TT were similar between the younger (18-64 years) and older (≥65 years) groups in the direct method, with combined reference intervals of 23.7-31.2 seconds, 10.4-12.8 seconds, and 14.7-17.5 seconds, respectively. However, there was a significant difference in Fib levels, with reference intervals of 1.7-4.5 g/L (18-64 years) and 2.1-4.6 g/L (≥65 years). The indirect method yielded reference intervals similar to the direct method: APTT 23.8-31.4 seconds, PT 10.4-13.0 seconds, TT 14.5-17.4 seconds, and Fib 1.8-4.3 g/L (18-64 years) and 2.0-4.5 g/L (≥65 years). For relatively healthy patients in the Colorectal Surgery department, the reference intervals from both methods were comparable, but significant differences were observed among Emergency Department patients. The reference intervals established in this study are more representative of the hospital's patient population. The indirect method showed high consistency with the direct method in relatively healthy individuals, indicating it can serve as an effective alternative.