Adaptation and validation of the Portuguese version of the Lithium Knowledge Test (LKT) of bipolar patients treated with lithium: cross-over study

OBJECTIVE: Adherence problems are a common feature among bipolar patients. A recent study showed that lithium knowledge was the main difference between adherent and non adherents bipolar patients. The Lithium Knowledge Test (LKT), a brief questionnaire, was developed as a means of identifying aspects of patients' practical and pharmacological knowledge which are important if therapy is to be safe and effective. The original English version is validated in psychiatric population, but a validated Portuguese one is not yet available. METHODS: One hundred six patients selected were diagnosed with bipolar disorder (I or II) according to DSM-IV criteria and had to be on lithium treatment for at least one month. The LKT was administered on only one occasion. We analysed the internal consis tency, concurrent validity, sensitivity and specificity of the LKT for the detection of the knowledge about lithium treatment of bipolar patients. RESULTS: The internal consistency, evaluated by Cronbach's alpha was 0.596. The mean of total score LKT by bipolar patients was 9.0 (SD: 0.75) for men and 8.74 (SD: 0.44) for women. Concurrent validity based on plasma lithium concentration showed a significant correlation between the total LKT score and plasma lithium (r = 0,232; p = 0.020). The sensitivity was 84% and specificity was 81%. CONCLUSION: LKT is a rapid, reliable instrument which appears to be as effective as a lengthier standard interview with a lithium clinic doctor, and which has a high level of acceptability to lithium patients. We found that the psychometric assessment of the Portuguese version of LKT showed good internal consistency, sensitivity and specificity.