Lin 2005.

Study characteristics
Patient sampling	Primary objective: to investigate the role of interleukin‐16 (IL‐16) in the pathogenesis of endometriosis Participants: women with suspected endometriosis who underwent laparoscopy Selection criteria: exclusion criteria: autoimmune diseases, no steroid treatment or immunosuppressant treatment 6 months prior to surgery Study design: cross‐sectional, single‐gate design, prospective collection of samples
Patient characteristics and setting	Clinical presentation: not specified Age: mean age 37 ± 10.3 years (endometriosis group), 36.8 ± 12.1 years (controls) Number of participants enrolled: 44 participants Number of participants available for analysis: 44 participants (cycle phase not reported) Setting: Department of O&G, College of Medicine, Zhejiang University Place of study: Hangzhou, China Period of study: September 2001 ‐ June 2002 Language: Chinese
Index tests	Index test: IL‐16 Details of the index test procedure as stated: serum IL‐16 was measured with enzyme‐linked immunosorbent assay (ELISA) (human IL‐16 BMS 248, Bender Medsystems, Vienna, Austria); no working ranges were reported; sample handling described Threshold for positive result: not provided Examiners: no information provided; unclear if blinded to the result of reference standard Interobserver variability: CV < 10%
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n = 22/44 (50%): stage I‐II 8, stage III‐IV 14; controls n = 22 Reference standard: laparoscopy/laparotomy N = 44 (100%) + histology Description of positive case definition by reference standard test as reported: visual inspection confirmed by histopathology; staging according to the rASRM classification Examiners: no information provided
Flow and timing	Time interval between index test and reference standard: blood samples were collected on the day of surgery Withdrawals: none
Comparative
Key conclusions by the authors	Reduced levels of IL‐16 in peritoneal fluid and serum of women with advanced stage endometriosis may imply a role of IL‐16 in the development and progression of endometriosis.
Conflict of interest	Not reported
Notes	The data for markers measured in peritoneal fluid are not reported in this review For IL‐16 there was no statistically significant difference between the groups ‐ no data available for meta‐analysis
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Did the study avoid inappropriate exclusions?	Yes
Was a 'two‐gate' design avoided?	Yes
		Unclear	Low
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?	No
		High	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