A screening questionnaire for generalized tonic-clonic seizures: Hospital-based validation vs field-validation method

The majority of the screening questionnaires for epilepsy have been validated in hospital settings. We previously developed and used for field validation a screening tool to detect generalized tonic-clonic seizures (GTCS) in the rural communities of the Chaco region of Bolivia. The objective of the present study was to perform a hospital-based validation of the same questionnaire and to compare the levels of accuracy obtained when validated in the field or in a hospital-based context. We carried out a hospital-based validation in the Hospital Hernandez Vera of Santa Cruz, Bolivia, where we enrolled patients affected by epilepsy with GTCS and controls. Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated. One hundred twenty questionnaires were administered to 59 patients (27 men [45.8%]; mean age +/- SD = 32.4 +/- 14.2 years) and 61 controls (27 men [44.3%]; mean age +/- SD = 32.6 +/- 14.3 years). We obtained levels of accuracy of 100%. Sensitivity and PPV were significantly higher than the estimates obtained in the field-validation study (sensitivity 100% vs 76.3%; PPV 100% vs 69.0%). Our screening questionnaire showed a significantly lower level of sensitivity when validated in the field, confirming that hospital-based validation can lead to an overestimation of sensitivity.