Rakhila 2013.

Study characteristics
Patient sampling	Primary objective: to investigate prostaglandin (PG) biosynthesis and catabolism pathways in eutopic and ectopic endometrium of women with endometriosis Participants: women undergoing laparoscopy for pelvic pain, infertility or both (endometriosis group) and women scheduled for tubal ligation Selection criteria: exclusion criteria: no other pelvic pathology, signs of endometrial hyperplasia, or neoplasia and any nonsteroidal anti‐inflammatory drugs (NSAIDs) or hormonal medication for 3 months before surgery Study design: observational two‐gate, prospective recruitment and sample collection
Patient characteristics and setting	Clinical presentation: endometriosis group ‐ chronic pelvic pain, infertility or both; controls – disease‐free women requesting tubal ligation Age: Mean age 34.2 ± 3.6 yeas (endometriosis group), 35.3 ± 3.8 years (controls) Number enrolled: 74 women Number available for analysis: 74 women (34 in proliferative and 40 in secretory cycle phase) Setting: Centre Hospitalier Universitaire de Québec, Hôpital Saint‐François d'Assise Place of study: Quebec, Canada Period of study: not specified Language: English
Index tests	Index test: prostaglandin synthases: Cox‐1, Cox‐2, mPGES‐1, mPGES‐2, cPGES, AKR‐1B1, AKR‐1C3; prostaglandin catabolic enzyme 15‐PGDH mRNA Description of positive case definition by index test as reported: expression levels of the biomarkers by RT‐PCR (using SYBR Green chemistry, carried out in ABI 7000 Thermal Cycler (Applied Biosystems); quantification by using a relative quantification method, normalised to GAPDH mRNA levels); sample handling and laboratory technique described Examiners: no information provided Interobserver variability: not reported
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n/N = 45/74 (61%); stage I‐IV, number per subgroup not provided; controls 29 Reference standard: laparoscopy Description of positive case definition by reference test as reported: staging according to the rASRM system Examiners: no information provided
Flow and timing	Time interval between index test and reference standard: tissue samples were obtained at laparoscopy Withdrawals: none reported
Comparative
Notes	Conclusion: This study reveals for the first time multiple defects in PG biosynthesis pathways, which differ between eutopic intrauterine and ectopic endometrial tissues and may, owing to the wide spectrum of PG properties, contribute to the initial steps of endometrial tissue growth and development and have an important role to play in the pathogenesis and symptoms of this disease Comments: For Cox‐1, cPGES, Akr1B1, Akr1C3 and 15‐PGDH mRNA there was no statistically significant difference between the groups ‐ no data available for meta‐analysis (Appendix 7) For Cox‐2, mPGES1 and mPGES2 mRNA there was a statistically significant difference between the groups, but there were insufficient data to construct 2 × 2 tables; not included 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 menstrual cycle phase considered in interpreting the 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