Borkowski 2008.

Study characteristics
Patient sampling	Primary objective: to evaluate total serum and peritoneal concentrations of vitamin D‐binding protein in women with endometriosis, known as an inflammation‐associated disease Participants: women undergoing surgical visualisation because of pain, infertility or both Selection criteria: inclusion criteria: pre‐menopausal age, regular cycle (25‐32 days) Study design: cross‐sectional, single‐gate design, prospective collection of samples
Patient characteristics and setting	Clinical presentation: pelvic pain, infertility or both Age: range 21‐50 years Number of participants enrolled: 43 women Number of participants available for analysis: 43 women (all in follicular phase of the menstrual cycle) Setting: Department of O&G, Wrocław Medical University; Laboratory of Reproductive Immunology, Institute of Immunology and Experimental Therapy, Polish Academy of Sciences Place of study: Wrocław, Poland Period of study: not stated Language: English
Index tests	Index test: vitamin D‐binding protein Details of the index test procedure as stated: serum vitamin D‐binding protein was measured by using ELISA (using goat polyclonal antibody against human Gc globulin; absorbance at 490 nm was read by using a Bio‐Tek 340 EL spectrophotometer; data analysed with KC3 software (Bio‐Tek Instruments; Winooski, USA); concentration were calculated by interpolation from a six‐point logarithmic standard curve); sample processing and experiments described Threshold for positive result: not provided Examiners: no information provided; unclear if blinded to the result of reference standard Interobserver variability: intra‐ and interassay CV < 10% and < 15%
Target condition and reference standard(s)	Target condition: endometriosis Prevalence of target condition in the sample: n = 26/43 (61%): stage I‐II 11, stage III‐IV 15; controls n = 17 Reference standard: laparoscopy N = 43 (100%) + histology Description of positive case definition by reference standard as reported: visual inspection, confirmed by histopathology; staging according to the rASRM classification Examiners: no information provided
Flow and timing	Time interval between index test and reference standard: venous blood was collected before the induction of anaesthesia Withdrawals: none
Comparative
Key conclusions by the authors	Serum and peritoneal DBP concentrations are not affected in women with endometriosis; however, based on the latest published data, it is possible that both the serum and peritoneal concentrations of vitamin D‐binding protein may be dependent on Gc genotype, which results in differential modulation of monocyte/macrophage activity
Conflict of interest	Not reported; supported by grant No. 3P05E 077 24 from the Polish Ministry for Scientific Research and Information Technology
Notes	For vitamin D‐binding protein there was no statistically significant 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?	Unclear
Did the study avoid inappropriate exclusions?	Yes
Was a 'two‐gate' design avoided?	Yes
		Unclear	Low
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