WFDC2 and ovarian carcinoma: The research questions of our current meta-analysis were formulated according to the PICO tool, which stands for patients/populations/problems (cases of ovarian cancer), index test (in the meta-analysis, HE4 levels in serum and urine of subjects are used as index test; the cutoff value of HE4 was different in various studies depending upon the method used for measurement), comparator (gold standard was a biopsy and histopathological examination (HPE)), and outcome (the patient-oriented outcome was determined by pooled sensitivity and specificity).