Diagnostic accuracy of tongue coating in identifying acute appendicitis: a prospective cohort study

Acute appendicitis requires timely diagnosis. The diagnostic efficacy of tongue examination in making this diagnosis has not been established. This study investigates whether the Tongue Coating Index (TCI), a validated measure of tongue coating, can aid in diagnosing acute appendicitis.

We conducted a prospective cohort study (1 September 2018-31 December 2020) at a single Japanese hospital. Adults (≥20 years) with suspected acute appendicitis, presenting to either the emergency department or general outpatient clinic, were enrolled. Tongue images were taken at presentation; two independent examiners-unrelated to clinical care and blinded to patient data-later scored these images using the TCI. A composite reference standard (clinical findings, imaging, histopathology, follow-up) was used to confirm appendicitis. We compared the TCI's diagnostic performance with the Alvarado score and its components using C-index, area under the curve (AUC), sensitivity and specificity.

Of 145 included patients, 69 (47.6%) were diagnosed with acute appendicitis. The TCI demonstrated comparable discriminative ability (C-index AUC 0.62; 95% CI, 0.53 to 0.71) to that of the Alvarado score (0.66; 95% CI, 0.57 to 0.75). Of Alvarado score components, migration of pain had an AUC of 0.63 (95% CI, 0.55 to 0.71), anorexia 0.58 (95% CI, 0.50 to 0.66) and tenderness in the right lower quadrant 0.55 (95% CI, 0.50 to 0.60). At a cut-off of 3, the TCI demonstrated high sensitivity of 96% (95% CI, 88% to 98%) but low specificity of 21% (95% CI, 13% to 32%). Conversely, at a cut-off of 10, the TCI showed increased specificity of 83% (95% CI, 73% to 90%) but reduced sensitivity of 29% (95% CI, 20% to 41%).

The TCI showed comparable diagnostic performance to the Alvarado score and its individual components. TCI may potentially serve as an additional non-invasive indicator for diagnosing or ruling out acute appendicitis. Further research is essential to validate its clinical utility.