Gagne 2003b.

Study characteristics
Patient sampling	Primary objective: to determine whether high levels of VEGF could also be found in the serum of patients with endometriosis Participants: women who were scheduled to undergo laparoscopy or laparotomy at 1 of the 8 clinical institutions in the Montreal area Selection criteria: inclusion criteria: pre‐menopausal age, no past pregnancy, luteal phase of the menstrual cycle (based on the last period and further confirmed by histology), regular cycles (21‐35 days), no acute salpingitis, no hormonal treatment or IUD in previous 3 months. Study design: multicentre study of two‐gate design, prospective recruitment, random sample of patients (participation rate > 90%)
Patient characteristics and setting	Clinical presentation: infertility (11% controls, 28% cases); pain (19% controls, 34% cases); tubal ligation (60% controls, 26% cases); hysterectomy (18% controls, 35% cases); diagnostic laparoscopy (22% controls, 39% cases); history of acute infections (30% controls, 34% cases); smoking (63% controls, 53% cases) Age: sampling from a population with mean age of 37.3 ± 6.4 years Number of participants enrolled: 277 women Number of participants available for analysis: 277 women (all in luteal cycle phase) Setting: biotech firm ‐ MetrioGene BioSciences (a subsidiary of PROCREA BioSciences) Place of study: Montreal, Canada Period of study: July 1997 ‐ May 2001 Language: English
Index tests	Index test: VEGF Details of the index test procedure as stated: serum VEGF levels were measured using a commercially available ELISA kit (R&D Systems, Minneapolis, MN) according to the manufacturer's instruction; assay sensitivity <9.0 pg/ml; sample handling and laboratory procedure described in details Threshold for positive result: not provided Examiners: no information provided; unclear if were blinded to the result of reference standard Interobserver variability: Inter‐ and intra‐assay CV <10%
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n = 131/277 (47%): stages I‐IV, numbers not specified; controls n = 146 Reference standard: laparoscopy/laparotomy N = 277 (100%) Description of positive case definition by reference standard test as reported: visual inspection; staging according to the ASRM classification Examiners: gynaecologists collaborating in the study were trained surgeons experienced with the management of endometriosis who were skilled in detecting and identifying all forms of endometriotic lesions
Flow and timing	Time interval between index test and reference standard: blood samples were collected before anaesthesia Withdrawals: none
Comparative
Key conclusions by the authors	Although VEGF seems to play a pivotal role locally in the implantation and development of endometriotic lesions, the disease is not associated with a significant modulation in the levels of circulating VEGF
Conflict of interest	Not reported (the authors' affiliation is MetrioGene BioSciences, a biotech firm)
Notes	For VEGF there was no 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?	Yes
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?	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