The Collaborative Ocular Tuberculosis Study (COTS) calculator-a consensus-based decision tool for initiating antitubercular therapy in ocular tuberculosis

Abstract

Objective: To introduce the Collaborative Ocular Tuberculosis Study (COTS) Calculator, an online clinical scoring system for initiating antitubercular therapy (ATT) in patients with ocular tuberculosis (TB).

Method: The COTS Calculator was derived from COTS Consensus (COTS CON) data, which has previously published consensus guidelines. Using a two-step Delphi method, 81 experts evaluated 486 clinical scenario-based questions, ranking their likelihood of initiating ATT in each specific scenario. Each scenario was a permutation of the results and/or availability of five following components-clinical phenotype, endemicity, two immunological (tuberculin skin test, interferon-γ release assay) and one radiological (chest X-Ray) test results-and a sixth component further stratifying three of the clinical phenotypes. The median scores and interquartile ranges (IQR) of each scenario were tabulated, representing the expert consensus on whether to initiate ATT in that scenario. The consensus table was encoded to develop the COTS Calculator.

Results: The COTS Calculator can be accessed online at: https://www.oculartb.net/cots-calc . The attending physician can select the conditions present in the patient, which will generate a median score from 1 to 5. 114 out of 486 scenarios (24%) deliberated had a median score of 5 indicating expert consensus to initiate ATT.

Conclusion: The COTS Calculator is an efficient, low-cost, evidence and experience-based clinical tool to guide ATT initiation. While it holds substantial promise in improving standard-of-care for ocular-TB patients, future validation studies can help to as certain its clinical utility and reliability.

Fig. 1. Flow chart depicting the number of clinical scenario-based questions reviewed in the Collaborative Ocular Tuberculosis Study Consensus (COTS CON) group Delphi Round 1 and 2, the clinical phenotypes reviewed in Delphi Round 2 phases 1 and 2, as well as the number of experts attending each discussion phase.

SLC serpiginous-like choroiditis, CS corticosteroids, AU anterior uveitis, IU intermediate uveitis, RV retinal vasculitis.

Fig. 2. Diagrammatic illustration of the ordinal score as entered by the experts and implication of median score and interquartile range (IQR).

ATT antitubercular therapy.

Fig. 3. The patient details that can be entered include patient name, patient identity document (ID) number, patient’s age, patient’s gender (male or female), patient’s physician name, the patient’s affected eye (left, right, or both eyes).

COTS CON collaborative ocular tuberculosis study consensus.

Fig. 4. The clinical phenotype selected is “retinal vasculitis” out of five options (anterior uveitis, intermediate uveitis, panuveitis, retinal vasculitis, choroiditis), which prompted an additional stratification of “active” disease to be selected amongst two options (active, inactive).

The endemicity of the patient selected is “endemic” out of two options (endemic, nonendemic). the tuberculin skin test/mantoux test, interferon gamma release assay (IGRA), and chest X-ray each has three options (positive, negative, not done/unknown) and “positive” was selected for all three. The combinations of these six selections corresponded to the result: Median Score “5” and Interquartile Range (IQR) “0”. TB tuberculosis, QFT-Gold Quantiferon-TB Gold, COTS collaborative ocular tuberculosis study. Two tables interpreting median score of 1–5 and Interquartile range (IQR) of 0–3 are presented. Median score 5 and IQR 0 and their interpretations are highlighted in yellow as corresponding to the patient’s conditions “Median score 5” is interpreted to be a very high probability for most experts to consider initiating Antitubercular therapy (81–100%). IQR 0 is interpreted to be representing absolute consensus, with more than 90% of experts agreeing on the initiation of antitubercular therapy.