Cross-Sectional and Longitudinal Construct Validity of the Generic KINDL-A(dult)B(rief) Questionnaire in Adults with Thrombophilia or with Hereditary and Acquired Bleeding Disorders.

Background/aims: The newly adapted generic KINDL-A(dult)B(rief) questionnaire showed satisfactory cross-sectional psychometric properties in adults with bleeding disorders or thrombophilia. This investigation aimed to evaluate its cross-sectional and longitudinal construct validity.

Methods: After ethical committee approval and written informed consent, 335 patients (mean age 51.8 ± 16.6 years, 60% women) with either predominant thrombophilia (n = 260) or predominant bleeding disorders (n = 75) participated. At baseline, patients answered the KINDL-AB, the MOS 36-item Short-Form Health Survey (SF-36), and the EQ-5D-3L. A subgroup of 117 patients repeated the questionnaire after a median follow-up of 2.6 years (range: 0.4-3.5). A priori hypotheses were evaluated regarding convergent correlations between KINDL-AB overall well-being and specific subscales, EQ-5D-3L index values (EQ-IV), EQ-5D visual analog scale (EQ-VAS), and SF-36 subscales.

Results: Contrary to hypothesis, baseline correlations between the KINDL-AB and EQ-IV/EQ-VAS were all moderate while, as hypothesized, several KINDL-AB subscales and SF-36 subscales correlated strongly. At follow-up, no significant changes in all three instruments occurred. Correlations between instruments over the follow-up were mostly moderate and partially strong. Contrary to hypothesis but consistent with no significant changes in health-related quality of life, convergent correlations between changes in KINDL-AB overall well-being, physical and psychological well-being, and EQ-IV/EQ-VAS were all weak.

Conclusions: While repeated measures of KINDL-AB showed moderate to strong correlations, changes in KINDL-AB overall well-being and subscales correlated more weakly than expected with changes involving two established instruments of generic health status.