Saad 2014.

Study characteristics
Patient Sampling	Case‐control study; part of a prospective study evaluating clinical, topographic, tomographic, and biomechanical characteristics of people with keratoconus and keratoconus suspect at the Rothschild Foundation, Paris, France.
Patient characteristics and setting	Participants were grouped as follows. Normal group Preoperative LASIK with 4‐year follow‐up Clinically evident bilateral keratoconus Exclusion criteria: corneal scarring in the anterior or posterior segment.
Index tests	Discriminant analysis composed of 3 variables: the difference between steep and flat keratometry, the 3‐mm irregularity, and the anterior elevation of the thinnest point. The algorithm was developed to discriminate keratoconus eyes from normal eyes.
Target condition and reference standard(s)	All keratoconus eyes were diagnosed by 1 corneal specialist based on clinical and topographic signs.
Flow and timing	All participants received the same reference and index test. All data were included in a 2 × 2 table.
Comparative	Not applicable
Notes	No funding source mentioned.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	No
Could the selection of patients have introduced bias?		High risk
Are there concerns that the included patients and setting do not match the review question?			High
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 the model designed in an appropriate manner?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference standard
Is the reference standard likely to correctly classify the target condition?	No
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
Could the reference standard, its conduct, or its interpretation have introduced bias?		High risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and timing
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Low risk
DOMAIN 5: Comparative