Inclusion and exclusion criteria of studies
We used “pregnancy of unknown location[Title]” as free text search
strings to search all studies diagnosed as PUL in MEDLINE, web of
science and Embase at the first visit. All studies exploring PUL
outcomes can be included. Other studies related to pregnancy diagnosis
were excluded. The eligibility criteria were as follows: (a) the study
population was adult patients diagnosed as PUL; (b) the diagnosis of
ectopic pregnancy was confirmed by ultrasound, non-visualized treatment
(increase in hCG after uterine evacuation) or surgery; and (c) data
regarding the true-positive (TP), false-positive (FP), false-negative
(FN) and true-negative (TN) rates can be found either directly or
indirectly in all studies. All prospective or retrospective randomized
controlled trials, case-control studies, cohort studies and
observational studies met the inclusion. All reviews, meta-analyses,
poster or oral meeting presentation, case reports, letters, responses or
comments, and non-English written studies were excluded. The studies
before 1984 was excluded, because transvaginal ultrasound had not been a
routine test for early pregnancy evaluation before
that8.