Tang 2009.

Study characteristics
Patient sampling	Primary objective: to investigate the possible roles of cyclin B1, cyclin‐dependent kinase (cdc2) and Polo‐like kinase 1 (Plk1) in the pathogenesis of endometriosis Participants: women who were undergoing laparoscopic surgery or hysterectomy Selection criteria: inclusion criteria: regular menstrual cycles (21–35 days), not on hormonal treatment, not pregnant, not breastfeeding, and not using IUD in the past 6/12 months; exclusion criteria: PID, adenomyosis, DUB Study design: observational study, two‐gate design, prospective sample collection
Patient characteristics and setting	Clinical presentation: not specified Age: range 24‐46 years Number enrolled: 59 women Number available for analysis: 50 women (27 in proliferative and 23 in secretory cycle phase) Setting: university hospital ‐ Women’s Hospital of Zhejiang University Medical School Place of study: Hangzhou, Zhejiang, China Period of study: 2005‐2006 Language: English
Index tests	Index test: cyclin B1, cdc2, Plk1 mRNA and protein Description of positive case definition by index test as reported: mRNA expression by RT‐PCR (using multiscribe reverse transcriptase (Invitrogen), single tube reaction with amplification; β‐actin gene used as internal reference); protein levels detected by Western Blot (Bradford assay (Bio‐Rad Laboratories, CA), normalised to β‐actin); laboratory technique described; thresholds not provided 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 = 20/50 (40%): all stages II‐III; controls 30 Reference standard: laparoscopy/laparotomy Description of positive case definition by reference test as reported: staging according to rAFS Examiners: none stated
Flow and timing	Time interval between index test and reference standard: not stated; the context suggests timing around surgery Withdrawals: 9 participants were not included in the analyses, reasons not explained
Comparative
Notes	Conclusion: the increased expression of cyclin B1, cdc2, and Plk1 in ectopic endometrium may be involved in the up‐regulated proliferation activity and neoplastic features of endometriosis. Comment: For Cyclin B1, cdc2, Plk1 mRNA and protein, 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?	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?	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?	Unclear
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	No
		High