A district health officer in Tamil Nadu is evaluating the impact of a new hypertension screening program launched 6 months ago. Before the program, the recorded prevalence of hypertension was 15% (based on hospital records). After 6 months of intensive community screening, the prevalence has risen to 22%. The officer suspects this reflects successful case detection. What is the most appropriate next step to confirm whether the increase in prevalence is due to improved detection versus a true increase in incidence of hypertension?