Objective: The aim of this study was to establish the specificity and sensitivity of a simplified screening test based on diastolic blood pressure and waist circumference for predicting metabolic syndrome. Method: Demographic, anthropometric (waist circumference and systolic and diastolic blood pressure) and laboratory (triglyceride, high-density lipoprotein and fasting glucose) data were collected from a large cohort of Dutch patients with a schizophrenia spectrum disorder in order to determine whether patients fulfilled the Western criteria of the International Diabetes Federation (IDF) for metabolic syndrome. The sensitivity, specificity, likelihood ratio of a positive or negative test outcome and positive and negative predictive values of the simplified test (only waist circumference and diastolic blood pressure) were calculated. Results: Of 252 recruited patients, 55% met the IDF criteria for metabolic syndrome. The sensitivity and the specificity of the simplified test were 65% and 85%, respectively. The likelihood ratios of positive and negative test outcomes were 4.35 and 0.41, respectively, and the positive and negative predictive values were 87% and 67%, respectively. Conclusion: This simplified screening test did not have diagnostic validity for metabolic syndrome in a Dutch cohort of patients with schizophrenia spectrum disorder.