Psychometric Testing of the THLA-W+ and Health Literacy among Service Recipients from Outpatient Departments of Public Hospitals in Nakhon Si Thammarat

Abstract

Objective: 1) To test validity and reliability of the Thai Health Literacy Assessment Using Word List with Extended Questions to Test Comprehension (THLA-W+), 2) to determine cut-off used to interpret the HL level measured by the THLA-W+ and 3) to find the percentage of service recipients from outpatient departments of Public Hospitals in Nakhon Si Thammarat with inadequate HL. Methods: Test of validity and reliability of the THLA-W+ was conducted in 1,003 patients from two Public Hospitals. Validity was tested by determining the difference of THLA-W+ scores among subjects with different education levels, and assessing relationship between the THLA-W+ and the understanding of drug labels and appointment cards, some questions from the Thai Health Literacy Skill Assessment (THLA-S) and the Thai Health Literacy Assessment Instrument: Nutrition Label (THLA-N8). The study used the receiver operating characteristics (ROC) curve analysis to find the cut-off using the understanding score on the drug label and appointment card, the combined score of understanding of drug labels and appointment cards and the ability to answer questions from the THLA-S and the THLA-N8 score as gold standard. The study estimated the percentage of patients with inadequate HL in 1,102 subjects from 23 public hospitals in Nakhon Si Thammarat. Results: Calculation of the THLA-W+ scores was in 3 forms: 1) reading test: THLA-W+R 2) comprehension test: THLA-W+RC 3) reading and comprehension test: THLA-W+RC). Reliability coefficient of the THLA-W+ was 0.90, 0.89 and 0.91 respectively. The test was valid with those with higher education levels having a higher THLA-W+ score in all 3 calculation methods (P <0.001). THLA-W+ had a significant positive correlation with the 3 HL indicators (r = 0.30-0.55). ROC curve analysis shows that THLA-W+C and THLA-W+RC had an area under the curve between 0.70-0.79. The cut points for THLA-W+R, THLA-W+C and THLA-W+RC were 46, 39 and 37, respectively. Sensitivity was 66.06-66.81, 69.84-72.15 and 66.30-68.39 respectively. Specificity was 57.23-73.91, 56.31-70.11 and 62.46-77.72 respectively. 46.5% of service recipients from outpatient departments in the public hospitals in Nakhon Si Thammarat province showed inadequate HL when evaluated with THLA-W + C. Conclusion: Overall, the THLA-W + scale was accurate, accurate, sensitive and specific. 46.5% of out-patients in the public hospitals in Nakhon Si Thammarat province showed inadequate HL.