Van der Linden 1995.

Study characteristics
Patient sampling	Primary objective: to examine the immunohistochemical properties of epithelial cells in peritoneal fluid and to compare the staining characteristics with cells of endometrium, menstrual effluent, peritoneum, and endometriotic lesions Participants: women who underwent a diagnostic laparoscopy as part of a subfertility work‐up Selection criteria: inclusion criteria: regular ovulatory cycles Study design: observational single‐gate, prospective sample collection
Patient characteristics and setting	Clinical presentation: infertility Age: reproductive age, not specified Number enrolled: 16 women Number available for analysis: 16 women (all in early proliferative cycle phase) Setting: tertiary care university medical centre ‐ the University of Limburg Place of study: Maastricht, the Netherlands Period of study: not reported Language: English
Index tests	Index test: vimentin, cytokeratin 18, cytokeratin 19 and endometrial epithelial marker BW 495/36 in menstrual fluid and endometrium Description of positive case definition by index test as reported: positive IHC staining; laboratory technique described Examiners: none stated; unclear if blinded to the result of reference standard Interobserver variability: not reported
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n/N = 8/16 (50%): all stage I; controls 8 Reference standard: laparoscopy + histology Description of positive case definition by reference test as reported: visual inspection confirmed by histopathology, staging according to rAFS Examiners: none stated
Flow and timing	Time interval between index test and reference standard: samples were collected at surgery Withdrawals: none reported
Comparative
Notes	Conclusion: These results support the contention of transport of menstrual detritus to the peritoneal cavity in women with patent fallopian tubes. Comment: For vimentin, cytokeratin 18, cytokeratin 19 and endometrial epithelial marker BW 495/36, there was no statistically significant difference between the groups ‐ no data available for meta‐analysis (Appendix 7)
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?	Unclear
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?	Yes
Was a menstrual cycle phase considered in interpreting the index test	Yes
		Unclear	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
		Low	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