Although a range of generic and diabetes-specific instruments are available to assess emotional distress, no studies have evaluated sensitivity in relation to sample size requirement. The present study sets out to compare the sensitivity among the Diabetes Health Profile Psychological Distress scale (DHP-PD), Problem Areas in Diabetes (PAID) and Kessler-10 Psychological Distress scale (K10). We hypothesized that the diabetes-specific measures (DHP-PD and PAID) would require smaller sample sizes than the generic measure (K10), yet remain specific.
A total of 208 patients with type 2 diabetes mellitus (mean age 45.2 (12.4) years; 63.1 % males, 45.8 % Chinese, 11.3 % Malay and 26.6 % Indian), recruited from a Singapore tertiary hospital diabetes clinic, completed the English DHP-PD, PAID and K10. Clinical information derived from medical records and HbA1c was recorded. Effect sizes (ES), ratio of ES and sample size requirement relative to the most sensitive questionnaire were computed.
A comparison of patients with good versus poor glycaemic control (HbA1c ≥7.0) revealed that using K10 will require 4 times the sample size of a study using the PAID in order to detect the same level of psychological distress. The DHP-PD and PAID had similar sensitivity when comparing between patients with good versus poor glycaemic control.
As hypothesized, sample size requirement is largest for K10 and remarkably similar for PAID and DHP-PD. This information is useful for designing clinical trials and studies.