Comparison of Analytical Values after Changing to the International Standardized Method for Lactate Dehydrogenase and Alkaline Phosphatase Measurements in Mouse and Rat

SIMPLE SUMMARY: Since April 2020 in Japan, lactate dehydrogenase and alkaline phosphatase assays, which were earlier conducted using the Japan Society of Clinical Chemistry protocols, are being conducted using the International Federation of Clinical Chemistry and Laboratory Medicine protocols. The correlation between blood values measured by these methods is not known in some species; therefore, values measured using these two methods cannot be used interchangeably. In this study, the relationship between lactate dehydrogenase and alkaline phosphatase values of mice and rats using each method was determined, and coefficients were generated to convert and compare the obtained values. These coefficients can be used for the mutual conversion of measured values during the transition period from the Japan Society of Clinical Chemistry method to the International Federation of Clinical Chemistry and Laboratory Medicine method. However, it should be noted that the conversion coefficients were affected by isozyme composition. ABSTRACT: Since April 2020, the method for lactate dehydrogenase (LD) and alkaline phosphatase (ALP) activity measurements in Japan has been switched from the Japan Society of Clinical Chemistry (JSCC) reference method, which is only used in Japan, to the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference method. However, in some species, the relationship between the blood values of both enzymes measured by the two methods remains unclear. Hence, values measured by these two methods cannot be used interchangeably. Therefore, this relationship was examined in ICR mice and Wistar/ST rats. The LD and ALP values obtained by both methods were plotted on scatter graphs, and regression equations were obtained. To compare the JSCC (x) and IFCC (y) methods, regression equations were generated for LD values in non-hemolytic samples as follows: y = 0.954x − 4.008 for ICR mice and y = 0.963x − 6.324 for Wistar/ST rats. The conversion factors from the JSCC to the IFCC methods were 0.954 (mice) and 0.963 (rats). The conversion coefficients from the IFCC to the JSCC methods were 1.048 (mice) and 1.088 (rats). For ALP values in fasted mouse and rat samples, the regression equations were y = 0.336x − 2.247 and y = 0.314x − 17.626, respectively. The conversion factors from the JSCC to the IFCC methods were 0.336 (mice) and 0.314 (rats). The conversion coefficients from the IFCC to the JSCC methods were 2.978 (mice) and 3.188 (rats). These conversion factors can be used for the mutual conversion of both measured values during the transition period from the JSCC to the IFCC method. However, it should be noted that the conversion coefficients for both LD and ALP were affected by isozyme composition.