Diagnostic validity of monothermal caloric screening test: a large-scale comparative study with bithermal standards

Objectives: This study aimed to assess the diagnostic performance of the monothermal caloric screening test (MCST) compared with the bithermal caloric test (BCT) for detecting vestibular asymmetry and to compare diagnostic performance between warm and cool stimulation as well as between air and water irrigation.Methods: This retrospective study analyzed 971 consecutive patients who underwent caloric testing (470 air, 501 water). Diagnostic performance of warm MCST and cool MCST was evaluated using BCT canal paresis (CP) thresholds of ≥20% and ≥25% as reference standards. Correlation and directional agreement were assessed using Pearson correlation and Cohen’s κ.Results: Warm MCST demonstrated superior diagnostic performance with a sensitivity of 97.4%, specificity of 58.5%, negative predictive value (NPV) of 98.3%, and the area under the curve (AUC) of 0.948 at a CP ≥25% threshold. Cool MCST showed comparable sensitivity (96.0%) but lower specificity (37.6%) and AUC (0.915). Bithermal CP correlated very strongly with warm monothermal caloric asymmetry (MCA) (r=0.95) versus moderately with cool MCA (r=0.90), with substantial directional agreement for warm (κ=0.65) but only moderate for cool (κ=0.49). Warm stimulation elicited significantly greater responses than cool (26.97%±27.2% vs. 22.82%±25.5%, <i>p</i><0.001). Air and water showed equivalent performance for warm testing (AUC, 0.939 vs. 0.953; <i>p</i>>0.2), whereas water was superior for cool testing (<i>p</i>=0.029).Conclusions: Monothermal warm caloric testing provides excellent screening accuracy (sensitivity and NPV >95%) with strong concordance to bithermal testing. Warm MCST can be recommended as a first-line screening tool, with complete bithermal testing reserved for positive cases requiring detailed quantification.