What are quality of life improvements measuring and do they last? An explanatory model

Selecting a subjective health status measure for optimum utility in everyday orthopaedic practice

BACKGROUND

The time required to complete patient outcome questionnaires such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Short Form General Health Survey (SF-36) and the Musculoskeletal Function Assessment (MFA) can sometimes threaten elderly, compromised patients sufficiently to compromise compliance with follow-up clinics. Incomplete questionnaires can also present problems of data bias. A little used (in the USA), patient-friendly questionnaire, the Nottingham Health Profile (NHP) has the potential to reduce the statistical and practical problems associated with the more generally used instruments. We hypothesized that NHP will produce similar results to WOMAC and SF-36 and is more sensitive to small changes in patient outcomes than SF-36 and MFA.

METHOD

Twenty-three patients blindly completed WOMAC, SF-36 and NHP questionnaires. Spearman's Rank Order Correlation was used to compare the component scores of each instrument. Simulation of the before and after results of 10 fictitious patient comparing MFA and NHP was conducted using the related sample t-test.

RESULTS

Seven of nine correlation coefficients were statistically significant and ranged from 0.711 to 0.901. The significance of the before and after difference on the five-point scale response was P = 0.05 when the NHP was used and P = 0.07 when MFA was used. The before and after difference on 'yes-no' response questions was P < 0.001 when NHP was used but showed no difference when the MFA was used.

CONCLUSIONS

Our hypothesis was supported and we suggest that NHP can be used with confidence as an alternative to other patient outcome instruments.