Bokor 2009.

Study characteristics
Patient sampling	Primary objective: to assess density of sensory small‐diameter nerve fibres in the functional layer of endometrium in women with minimal to mild endometriosis and in women with a normal pelvis in order to develop a possible semi‐invasive diagnostic tool for minimal to mild endometriosis Participants: endometrial samples selected from tissue bank, which were collected from women undergoing laparoscopies for infertility, pain or both Selection criteria: inclusion criteria: no medical treatment for 3/12 months preceding surgery, secretory phase of menstrual cycle Study design: observational single‐gate design, prospective sample collection, retrospective selection of cases
Patient characteristics and setting	Clinical presentation: infertility, 100%; dysmenorrhoea, 25% Age: mean age 33 ± 10 years, endometriosis; 32 ± 5 years, controls Number enrolled: 40 women (retrospective selection) Number available for analysis: 40 women (all in secretory phase of menstrual cycle) Setting: University Hospital Gasthuisberg Place of study: Leuven, Belgium Period of study: not provided Language: English
Index tests	Index test: endometrial neural markers: PGP 9.5, VIP, CGRP, SP, NPY, NF Description of positive case definition by index test as reported: nerve fibre density was defined as total number of nerve fibres divided by the total surface area of the examined endometrium; nerve fibres were evaluated by IHC for each marker and counted in HPF areas for the slide section (antibody detection with REAL Detection System, Alkaline Phosphatase/RED, Rabbit/Mouse (Dako); analysis by image analysis software KS400 3.0 (Zeiss, Germany) linked to a Zeiss microscope); the whole surface of each section was evaluated on high‐power images; procedure described; thresholds not pre‐specified; reported cut‐off values: PGP 9.5 − 0.49, VIP − 0.08, CGRP − 0.23, SP − 0.2, NPY − 0.13, NF − 0.19 Examiners: 1 examiner who was blinded to the diagnosis Interobserver variability: NA
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n/N = 20/40 (50%), all stage I‐II Reference standard: laparoscopy + histology Description of positive case definition by reference test as reported: laparoscopically and histologically confirmed endometriosis, staged according to rASRM Examiners: none mentioned
Flow and timing	TIme interval between index test and reference standard: prior to laparoscopy Withdrawals: none reported
Comparative
Notes	Conclusion: The combined analysis of neural markers PGP 9.5, VIP and SP could predict the presence of minimal to mild endometriosis with 95% sensitivity, 100% specificity and 97.5% accuracy. Prospective studies are required to confirm our findings.
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?	Yes
		High	Low
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
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?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
		Low