The objective of the present study was to evaluate the performance of the monothermal caloric screening test in a large sample of patients.
A retrospective analysis of the medical records of 1002 consecutive patients who had undergone vestibular assessment at the Mayo Clinic during the years 1989 and 1990 was conducted. Patients with incomplete alternate binaural bithermal (ABB) caloric testing, congenital or periodic alternating nystagmus, or bilateral vestibular loss were excluded from the study. Clinical decision theory analyses (relative operating characteristic curves) were used to determine the accuracy with which the monothermal warm (MWST) and monothermal cool (MCST) caloric screening tests predicted the results of the ABB caloric test. Cumulative distributions were constructed as a function of the cutoff points for monothermal interear difference (IED) to select the cutoff point associated with any combination of true-positive and false-positive rates.
Both MWST and MCST performed well above chance level. The test performance for the MWST was significantly better than that of the MCST for three of the four ABB gold standards. A 10% IED cutoff point for the MWST yielded a false-negative rate of either 1% (UW ≥25%) or 3% (UW ≥20%). The use of a 10% IED (UW ≥25%) for the MWST would have resulted in a 40% reduction (N = 294) in the number of ABB caloric tests performed on patients without a unilateral weakness.
The results of this study indicated that the MWST decreases test time without sacrificing the sensitivity of the ABB caloric test.
The alternate binaural bithermal (ABB) caloric test can be shortened by irrigating each ear using a single temperature (i.e., monothermal warm screening test or MWST) and discontinuing the test if responses are symmetric. The goal of the MWST is to decrease test time and increase patient comfort without sacrificing the sensitivity of the ABB caloric test. The present study evaluated the performance of the MWST using ROC curves and several gold standards for unilateral weakness on the ABB caloric test. The results indicate that the use of a 10% inter-ear difference produces clinically acceptable false-negative rates (1-3%) and reduces the number of unnecessary ABB caloric tests.
1Vestibular Research Laboratory, James H. Quillen VA Medical Center, Mountain Home, Tennessee; 2Department of Communicative Disorders, East Tennessee State University, Johnson City, Tennessee; 3Austin Medical Center – Mayo Health System, Austin, Minnesota; and 4Boystown National Research Hospital, Omaha, Nebraska.
This work was supported, in part, by Merit Reviews and the Auditory and Vestibular Dysfunction Research Enhancement Award to the first and second authors by the Rehabilitation Research and Development Service, Department of Veterans Affairs.
Portions of this paper were presented at the 1990 Midwinter Meeting of the Association for Research in Otolaryngology, St. Petersburg Beach, FL.
Address for correspondence: Owen D. Murnane, PhD, James H. Quillen VAMC, Audiology (126), Mountain Home, TN 37684. E-mail: email@example.com.
Received March 25, 2008; accepted November 15, 2008.