Gurgan 1990.

Study characteristics
Patient sampling	Primary objective: to evaluate possible value of peritoneal fluid CA‐125 levels as a more sensitive marker of minimal (stage I) endometriosis when compared to serum levels measured simultaneously Participants: women undergoing laparoscopy as part of infertility work‐up or tubal sterilisation Selection criteria: exclusion criteria: patients with more advanced endometriosis (> stage I) or other pathological findings Study design: cross‐sectional study of two‐gate design, prospective recruitment
Patient characteristics and setting	Clinical presentation: not specified Age: mean age 30.1 ± 2.6 years (endometriosis), 27.9 ± 2.6 years (controls) Number of participants enrolled: 38 women Number of participants available for analysis: 38 women (all in mid‐secretory phase of menstrual cycle) Setting: Department of Obstetrics and Gynaecology, Faculty of Medicine, University of Hacettepe Place of study: Sihiye‐Ankara, Turkey Period of study: October 1988 ‐ June 1989 Language: English
Index tests	Index test: CA‐125 Details of the index test procedure as stated: CA‐125 in serum and PF was measured in duplicates using an immunoradiometric assay assay (ELISA CA‐125, Compagnie ORIS Industrie, France); assay sensitivity 2.4 U/ml; sample handling and laboratory procedure described Threshold for positive result: > 16 U/ml, not pre‐specified Examiners: no information provided; unclear if were blinded to the result of reference standard Interobserver variability: Inter‐ and intra‐assay CV 5.7%‐8.1% and 2%‐10%
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n = 17/38 (45%) all stage I; controls n = 21 Reference standard: laparoscopy N = 38 (100%) Description of positive case definition by reference standard test as reported: classification according to the ASRM classification Examiners: no information provided
Flow and timing	Time interval between index test and reference standard: blood samples were collected immediately surgery Withdrawals: none
Comparative
Key conclusions by the authors	CA‐125 levels have been found to be mildly, but not significantly elevated in sera of patients with minimal endometriosis; laparoscopic evaluation remains the most reliable method of diagnosis of minimal endometriosis
Conflict of interest	Not reported
Notes	The data for markers measured in peritoneal fluid are not presented in this review
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
Was a 'two‐gate' design avoided?	No
		High	High
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	No
Was a cycle phase considered in interpretation of the result of index test?	Yes
		High	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Unclear
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
		Unclear	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
		Low