Bessho 2006.

Study characteristics
Patient Sampling	Retrospective, multicentre, case‐control study. 165 eyes of 120 subjects were included at 2 centres in Japan.
Patient characteristics and setting	People with keratoconus or keratoconus suspect comprised the keratoconus group. People with post‐photorefractive keratectomy or with‐the‐rule astigmatism and people without disease comprised the non‐keratoconus group.
Index tests	Fourier‐incorporated keratoconus detection Index (FKI) created performing a logistic regression analysis with a training set to differentiate the keratoconus group from the non‐keratoconus group. The index is based on information obtained by Fourier analysis from not only the anterior corneal surface but also from the posterior corneal surface and corneal thickness.
Target condition and reference standard(s)	Corneal topographic analysis was performed with a slit‐scanning corneal topographer (Orbscan II, Bausch & Lomb). It is unclear how the diagnosis was made; however, cases were classified before the inclusion.
Flow and timing	It is unclear if all cases received the same reference standard. All data were included in a 2 × 2 table.
Comparative	Not applicable
Notes	This study was supported in part by Grant‐in‐Aid No.15591854 for Scientific Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology (N. Maeda), and by a research grant from the Osaka Eye Bank Foundation, Suita, Japan (N. Maeda).
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	Unclear
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?	Unclear
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?		Unclear 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?	Unclear
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Unclear risk
DOMAIN 5: Comparative