Three new strategies to improve the accuracy of monothermal caloric screening testing

Objective: The objective was to find a way to estimate the value of inter-ear difference (IED) through monothermal caloric screening testing (MCST) that can be used at any laboratory, controlling and minimising the resulting error.

Methods: We retrospectively included in this study 2304 patients from our department to whom a videonystagmography with caloric testing was performed between 2003 and 2011. The IED was calculated in 3 different ways: Using the values of the 4 caloric stimulations (bithermal form) and using only the 2 same-temperature values (warm monothermal and cool monothermal forms). We studied 3 strategies to improve the accuracy of MCST: Analysis of variables that could impair the prediction, delimitation of a grey area of insufficient prediction and location of a maximum utility cut-off point.

Results: Correcting Jongkees' formula with the value for spontaneous nystagmus makes it possible to include subjects with spontaneous nystagmus or nystagmus inversion. Establishing 2 cut-off points to classify the subjects avoids approximately 38% of bithermal stimulations performed with a sensitivity and specificity of 95%. Maximum utility was obtained diagnosing as healthy those subjects with IED values lesser than or equal to 16% in warm MCST when the pathological IED was set as greater than 20%.

Conclusion: New statistical tools help clinicians to make decisions that affect their patients based on the results of MCST.