Tumor M2-PK was measured by ELISA (ScheBo[R] Biotech AG).
For each measurement point, the mean tumor M2-PK activity was calculated as the mean of duplicate determinations.
To estimate the potential impact of degradation of tumor M2-PK on the diagnostic accuracy of the test, results of stability testing were used in combination with fecal tumor M2-PK activities measured in 65 CRC patients (26 with colon cancer and 39 with rectal cancer) and in 917 unselected older adults.
The theoretical tumor M2-PK activity after n days of storage at room temperature was estimated as the relative activity after n days multiplied by the initial activity in CRC patients (to determine sensitivity) and of ESTHER study participants (to determine specificity).
Overall, 13 patients fulfilled the inclusion criteria (initial tumor M2-PK activity [greater than or equal to] 4 kU/L).
The potential impact of tumor M2-PK degradation on test performance characteristics is shown in Table 1.
We conclude that the handling of stool samples affects performance characteristics of the tumor M2-PK stool test.