MMP-7 could be detected in 54/60 menstrual blood samples
and was never detected in any of the control blood samples and
in the vaginal and semen samples when the cycle number did
not exceed 40 (Fig. 1). The control marker GAPDH was
positive in all samples (Fig. 2). The threshold cycle (CT)-values
for MMP-7 ranged between 25 and 37, for GAPDH between 24
and 34 (Fig. 3). Dilution experiments showed that for both
markers the amplification was linear and the detection limit was
CT = 39. Beyond this point samples were always negative
although mRNA (GAPDH with or without MMP-7) definitely
was present, yet strongly diluted. On the other hand, some nonmenstrual
samples reached the threshold fluorescence level for
MMP-7 at cycles 43–45 when the amplification was extended
to this cycle number.
The six false negative samples had CT-values for GAPDH of
29.8, 30.4, 33.6 (samples of day 1 of the menstrual cycle), 34.9
(day 2), 35.8 and 35.9 (day 4) and they belonged to four
different donors.