SummaryBackground: The conjunctival provocation test (CPT) is a diagnostic procedure for the assessment of allergic diseases. Photographs are taken before and after provocation increasing the redness of the conjunctiva due to hyperemia. Objective: We propose and evaluate an automatic image processing pipeline for objective and quantitative CPT. Method: After scale normalization based on intrinsic image features, the conjunctiva region of interest (ROI) is segmented combining thresholding, edge detection and Hough transform. Redness of the ROI is measured from 0 to 1 by the average pixel redness, which is defined by truncated projection in HSV space. In total, 92 images from an observational diagnostic study are processed for evaluation. The database contains images from two visits for assessment of the test-retest reliability (46 images per visit). Result: All images were successfully processed by the algorithm. The relative redness increment correlates between the two visits with Pearson's r = 0.672 (p < .001). Linear correlation of the automatic measure is larger than the manual measure (r = 0.59). This indicates a higher reproducibility and stability of the automatic method. Conclusion:We presented a robust and effective way to objectify CPT. The algorithm operates on low resolution, is fast and requires no manual input. Quantitative CPT measures can now be established as surrogate endpoint in controlled clinical trials.
Background: Allergen provocation tests are useful methods for proving the clinical relevance of an allergen-specific sensitization. Among these methods, the conjunctival provocation test (CPT) represents an easy-to-use tool. However, its readout parameters have not yet been internationally standardized or validated. Photodocumentation has been shown as a good option for objectifying a CPT reaction, supporting the local investigator assessment. Based on test-retest reliability of the score and an objective digital photoanalysis of the conjunctival redness, this study aimed to prove the reproducibility of a new CPT scoring system for use in clinical trials (ClinicalTrials.gov identifier: NCT02690740). Methods: A titrated quantitative CPT was conducted outside of the pollen season in a final cohort of 23 adult patients with birch or grass pollen-induced allergic rhinoconjunctivitis. Conjunctival symptoms were analyzed using a standardized symptom score. Conjunctival redness was also evaluated by an external observer and correlated with a digital photoanalysis using MATLAB software. Results: A test-retest correlation of 0.6 (p < 0.01) was found for the symptom score results. Likewise, a correlation of 0.65 (p < 0.01) was observed in the digital photoanalysis. The total symptom score showed a decrease in the mean value of 0.48 score points in the retest. Conclusions: This study reveals both a valuable test-retest correlation of the proposed score as well as a good correlation of eye redness with the (objective) photodocumentation. Based on our results, we can recommend the use of this scoring system as a valuable clinical protocol for future clinical trials.
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