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INTRODUCTION: Pseudobulbar affect (PBA) is described as uncontrolled, unprovoked outbursts of laughing and/or crying not related to the patient’s underlying emotion or experience. PBA may be overlooked or underdiagnosed and so an effective method of evaluation is important. The Center of Neurologic Study-lability Scale (CN-LS) is such a selfreport Likert scale consisting of seven questions on laughing and crying.
METHODS: The study was done to carry out the validity and reliability studies in Turkish for this test and validate it for multiple sclerosis (MS). For the content validity of the scale, one measurement and evaluation expert and five experts on the subject were interviewed. After a pilot study to evaluate the clarity of the scale, the reliability of the test was determined by sampling 154 normal and 56 MS patients, testing and retesting.
RESULTS: Test–retest correlations were high (Pearson correlation coefficient = 0.99, n = 56, p = .000). Also, there was no statistically significant difference between the means by using dependent sample t-test analysis (t = 0.40, n = 210, p = .69). In order to reveal the internal consistency of the test, the Cronbach alpha coefficient, another reliability test, was calculated and found to be high (α = 0.83, n = 210). For validation of the scale for MS, a separate study was conducted on 63 patients and ROC (receiver operating characteristic) analysis for criterion validity was performed. To define the cut-off score at or above which an individual with MS can be diagnosed as having PBA, one physician performed the test while the other independently stated his impression on the presence of the condition and the two scores were compared using the ROC analysis. The ROC curve analysis for the criterion validity was found to be very high (area under the curve = 0.976, p = .000). Using sensitivity and specificity calculations, the best acceptable cut-off score turned out to be 14.5 as being positive for PBA in Turkish MS patients.
CONCLUSION: Timely and appropriate evaluation of PBA is important in MS and the CNS-LS is a robust test instrument that has been used to assess PBA in different neurological conditions including MS. This condition has been known to influence the quality of life of patients. So after this study of validity, reliability, and validation, we hope it will be routinely used for evaluation.