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Published on: December 31, 2015
P Score: A Reference Image-Based Clinical Grading Scale for Vascular Change in Retinopathy of Prematurity
Gil Binenbaum1, Andreas Stahl2, Aaron S Coyner3
1Division of Ophthalmology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania.
Insights
A new 9-photograph reference set for grading plus-like vascular changes in retinopathy of prematurity (ROP) significantly improved intergrader agreement. This standardized P score enhances ROP assessment and communication among clinicians.
Area of Science:
- Ophthalmology
- Medical Imaging
- Neonatology
Background:
- Retinopathy of Prematurity (ROP) diagnosis relies on assessing vascular changes, historically with variable expert agreement.
- The International Classification of Retinopathy of Prematurity, Third Edition (ICROP3) recognizes plus-like vascular changes exist on a spectrum.
Purpose of the Study:
- To develop and validate a standardized 9-photograph reference set (P score) for grading plus-like vascular changes in ROP.
- To compare intergrader agreement using the P score versus standard grading (no plus, preplus, plus).
Main Methods:
- A consensus-based 9-photograph reference set (P1-P9) was created from fundus images representing increasing degrees of vascular tortuosity and dilation.
- 30 ophthalmologists with ROP expertise graded 150 fundus photographs using two methods: standard grading and the P score system.
- Intergrader agreement was measured using the intraclass correlation coefficient (ICC).
Main Results:
- Intergrader agreement was significantly higher with the P score (ICC = 0.75) compared to standard grading (ICC = 0.67).
- Mean P scores correlated with disease severity: 2.5 ± 0.7 for no plus, 4.8 ± 0.8 for preplus, and 7.4 ± 0.8 for plus disease.
Conclusions:
- The 9-photograph P score reference set demonstrates high intergrader agreement for assessing plus-like vascular changes in ROP.
- The P score is being incorporated into ICROP3 for clinical practice to improve consistency in ROP assessment, communication, and documentation.
- While not replacing clinical decisions, the P score aids in comparing examinations, facilitating communication, and potentially enhancing ROP classification for research.
Purpose:
The International Classification of Retinopathy of Prematurity, Third Edition (ICROP3), acknowledged that plus-like retinopathy of prematurity (ROP) vascular changes occurs along a spectrum. Historically, clinician-experts demonstrate variable agreement for plus diagnosis. We developed a 9-photograph reference image set for grading plus-like changes and compared intergrader agreement of the set with standard grading with no plus, preplus, and plus disease.
Design:
Retinal photographic grading and expert consensus opinion.
Participants:
The development set included 34 international ICROP3 committee members. The validation set included 30 ophthalmologists with ROP expertise (15 ICROP3 committee members and 15 non-ICROP3 members) METHODS: Nine ROP fundus images (P1 through P9) representing increasing degrees of zone I vascular tortuosity and dilation, based on the 34 ICROP3 committee members' gradings and consensus image reviews, were used to establish standard photographs for the plus (P) score. Study participants graded 150 fundus photographs 2 ways, separated by a 1-week washout period: (1) no plus, preplus, or plus disease and (2) choosing the closest P score image.
Main Outcome Measures:
Intergrader agreement measured by intraclass correlation coefficient.
Results:
Intergrader agreement was higher using the P score (intraclass correlation coefficient, 0.75; 95% confidence interval, 0.71-0.79) than no plus, preplus, or plus disease (intraclass correlation coefficient, 0.67; 95% confidence interval, 0.62-0.72). Mean ± standard deviation P scores for images with mode gradings of no plus, preplus, and plus disease were 2.5 ± 0.7, 4.8 ± 0.8, and 7.4 ± 0.8, respectively.
Conclusions:
Intergrader agreement of plus-like vascular change in ROP using the P score is high. We now incorporate this 9-image reference set into ICROP3 for use in clinician daily practice alongside zone, stage, and plus assessment. P score is not yet meant to replace plus diagnosis for treatment decisions, but its use at our institutions has permitted better comparison between examinations for progression and regression, communication between examiners, and documentation of vascular change without fundus imaging. P score also could provide more detailed ROP classification for clinical trials, consistent with the spectrum of plus-like change that is now formally part of the International Classification of Retinopathy of Prematurity.
Financial Disclosure(S):
Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
