| Study characteristics |
| Patient Sampling |
Single‐centre case‐control study in Spain, including 464 eyes of 464 participants |
| Patient characteristics and setting |
Participants were divided into the following 2 groups.
|
| Index tests |
A model of detection of early keratoconus (only grade 1) obtained by logistic regression considering the new parameters defined according to a new geometric approach |
| Target condition and reference standard(s) |
The standard criteria for keratoconus diagnosis were the presence of an asymmetric bowtie pattern in corneal topography, KISA% index ≥ 100%, a central keratometry with different cut‐off values to keratoconus suspect (> 47.2 D), an I‐S asymmetry with a cut‐off value of 1.4 D difference between average inferior and superior corneal powers at 3 mm from the centre of the cornea, as well as other topographic indices and ≥ 1 keratoconus sign on slit‐lamp examination, such as stromal thinning, conical protrusion on the cornea at the apex, Fleischer's ring, Vogt's striae, or anterior stromal scar. Corneal analysis was performed by the Sirius system (CSO, Italy). It seems that a single experienced examiner was involved in selection and classification. However, cases were classified before inclusion. |
| Flow and timing |
All cases were included in the reference standard and index test. All data were included in a 2 × 2 table. |
| Comparative |
Not applicable |
| Notes |
The study was carried out in the framework of the Thematic Network for Co‐Operative Research in Health (RETICS) reference number RD12/0034/0007 and RD16/0008/0012, financed by the Carlos III Health Institute ± General Subdirection of Networks and Cooperative Investigation Centers (R&D&I National Plan 2008±2011) and the European Regional Development Fund (FEDER). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. |
| 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? |
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? |
Unclear |
|
|
| Was the model designed in an appropriate manner? |
No |
|
|
| Could the conduct or interpretation of the index test have introduced bias? |
|
Unclear 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? |
Yes |
|
|
| Were all patients included in the analysis? |
Yes |
|
|
| Could the patient flow have introduced bias? |
|
Low risk |
|
| DOMAIN 5: Comparative |
