Imaging-based detection of anterior chamber inflammation: a comparative diagnostic accuracy study

Abstract

PurposeWe investigated the impact of operator parameters on the diagnostic performance of danterior segment optical coherence tomography (AS-OCT) in anterior uveitis. DesignProspective comparative diagnostic analysis. MethodsSetting: Single site.Study Population: Children aged under 18 years with anterior uveitis, recruited consecutively.Observation Procedures: Index testing: Optovue RTVue80 AS-OCT using ‘low-volume’ (LV, horizontal and vertical cross-sections) and ‘high-volume’ (HV, 68 horizontal cross-sections) protocols. Reference testing: slit lamp examination with anterior chamber inflammation graded using standardisation of uveitis nomenclature (SUN).Main Outcome Measure: Index test performance metrics (sensitivity, specificity, likelihood ratios), utility for ‘ruling-in’ and ‘ruling-out’ disease (positive / negative predictive values, PPV/NPV), receiver operating characteristic (ROC) curves to explore the impact of different imaging derived metrics, multivariable multilevel regression analyses to quantify correlation of index to reference testing, and repeatability indices across protocols. Results40 children (77 eyes: 51 eyes at SUN grade 0, 10 at SUN0.5+, 8 at SUN1+, 8 SUN≥2+ or higher) were included. There was high repeatability across protocols (0.98, p<0.001, 95% CI 0.75-1.0). OCT resulted in strong predictive values for ‘ruling-out’ (LV-scan NPV 82.9%, 95% CI 71.5 - 90.4%; HV-scan NPV 100%, 95% CI 3% to 100%), and but less predictive value for ‘ruling-in’ SUN≥0.5+ (LV-scan PPV 52.8% 95% CI 41.5 - 63.7%; HV-scan PPV 34.2%, 95% CI 33.3 to 35.1%). Detection of more than 1 cell within a cross sectional scan was strongly suggestive of clinical activity, with area under the curve of 0.76 (95% CI 0.62 - 0.89) for SUN≥0.5+, and 0.85 (95% CI 0.73- 0.98), for the detection of SUN≥1+. Cell count correlated with SUN grades at higher levels of inflammation (SUN≥2+ both protocols, SUN≥1+ HV-scans). There was an independent positive association between age and AS-OCT cell (adjusted correlation coefficient 0.2 cells for each additional year of age). ConclusionsOperator dependent factors impact the diagnostic and quantification performance of AS-OCT for anterior chamber inflammation. However, the strong, ‘dose-respondent’ correlation of low-volume protocols with SUN grading promises clinical utility without the storage and analysis burden of high-volume approaches. Further work will involve exploration of the need for age-specific image metric interpretation.