Liu 2008.

Study characteristics
Patient sampling	Primary objective: to investigate the distribution of ER isoforms in endometriosis and eutopic endometrium Participants: patients who underwent surgical treatment of ovarian endometrioma (study group) and total hysterectomy for cervical lesions in the authors' institution (controls) Selection criteria: inclusion criteria: regular menstrual cycle and no history of hormonal therapy 6 months prior to surgery Study design: cross‐sectional two‐gate, prospective collection of samples
Patient characteristics and setting	Clinical presentation: not specified Age: mean age 36 years (range 24‐49), endometriosis; 40 years (range 27‐46), controls Number enrolled: 90 women Number available for analysis: 90 women (45 in proliferative and 45 in secretory cycle phase) Setting: university hospital: Chinese People's Liberation Army General Hospital, affiliated to Peking Union Medical College Place of study: Beijing, China Period of study: January 2004 to December 2006 Language: Chinese
Index tests	Index test: ER‐α and ER‐β Description of positive case definition by index test as reported: positive expression of ER‐α and ER‐β was evaluated by IHC and classified by using Sinicrope Improved Semi‐quantitative Method (the percentage of stained cells and the intensity of staining was scored each by a 4 tier point system in each sliced section; both scores were added up and interpreted as: < 0.5 points means negative; 0.5‐1.5 points means weakly positive (+); 1.6‐2.5 points means averagely positive (++); > 2.5 points means strongly positive (+++).; laboratory technique described; threshold was not pre‐specified Examiners: no information provided Interobserver variability: not provided
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n/N = 60/90 (67%): stage not reported; controls 30 Reference standard: laparotomy/laparoscopy Description of positive case definition by reference test as reported: no information provided Examiners: no information provided
Flow and timing	TIme interval between index test and reference standard: samples were taken at surgery Withdrawals: none reported
Comparative
Notes	Conclusions: Both ER‐α and ER‐β have higher expression levels in eutopic endometrium of patients with ovarian endometriotic cysts. ER‐β is predominantly expressed in endometriotic cysts, whereas the expression of ER‐α is limited. The different distribution of ER‐α and ER‐β may play an important role in the development of ovarian endometriosis. Comments: The authors also report findings for endometriotic cysts; not included in this review The authors also report findings for each cycle phase; not presented 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