Rosa Lamarca

Classical test theory versus Rasch analysis for quality of life questionnaire reduction

BackgroundAlthough health-related quality of life (HRQOL) instruments may offer satisfactory results, their length often limits the extent to which they are actually applied in clinical practice. Efforts to develop short questionnaires have largely focused on reducing existing instruments. The approaches most frequently employed for this purpose rely on statistical procedures that are considered exponents of Classical Test Theory (CTT). Despite the popularity of CTT, two major conceptual limitations have been pointed out: the lack of an explicit ordered continuum of items that represent a unidimensional construct, and the lack of additivity of rating scale data. In contrast to the CTT approach, the Rasch model provides an alternative scaling methodology that enables the examination of the hierarchical structure, unidimensionality and additivity of HRQOL measures. METHODS: In order to empirically compare CTT and Rasch Analysis (RA) results, this paper presents the parallel reduction of a 38-item questionnaire, the Nottingham Health Profile (NHP), through the analysis of the responses of a sample of 9,419 individuals.ResultsCTT resulted in 20 items (4 dimensions) whereas RA in 22 items (2 dimensions). Both instruments showed similar characteristics under CTT requirements: item-total correlation ranged 0.45–0.75 for NHP20 and 0.46–0.68 for NHP22, while reliability ranged 0.82–0.93 and 0.87–94 respectively.ConclusionsDespite the differences in content, NHP20 and NHP22 convergent scores also showed high degrees of association (0.78–0.95). Although the unidimensional view of health of the NHP20 and NHP22 composite scores was also confirmed by RA, NHP20 dimensions failed to meet the goodness-of fit criteria established by the Rasch model, precluding the interval-level of measurement of its scores.

Treatment and quality of life in patients with chronic obstructive pulmonary disease

Treatments administered to patients with chronic obstructive pulmonary disease (COPD), especially when used in multiple combinations, are not free of interactions and side effects that can potentially impair health-related quality of life (HRQL). We studied HRQL and its relationship with treatment in a group of 441 patients with stage II or III COPD (age: 66.6 (SD: 8.3) years; FEV1: 32.4% (SD: 8.1%)) using the St Georges Respiratory Questionnaire (SGRQ) and the 12-item short form (SF-12) Health Survey. The most prescribed drugs were ipratropium bromide (87.5%), inhaled corticosteroids (69.4%) and short-acting β-2 agonists (64.9%). Patients with stage III of the disease were receiving more drugs, particularly short-acting β-2 agonists (p = 0.002) and inhaled corticosteroids (p = 0.031). The use of theophyllines was associated with a worse total SGRQ score (β = 4.49; p < 0.001), although this negative association decreased with advanced age. A trend towards worse SGRQ scores was observed with the use of high doses of long-acting β-2 agonists (β = 3.22; p = 0.072). Patients receiving three drugs or more presented worse total SGRQ scores than patients receiving fewer drugs (β = 6.1, p < 0.001; and β = 7.64, p < 0.001, respectively). These findings suggest that the use of multiple drugs in the treatment of patients with COPD is associated with worse total SGRQ scores. The effect of drugs, their dosages and associations with other drugs on HRQL merit further research.

Evolution of self-rated health status in the elderly: Cross-sectional vs. longitudinal estimates

We assessed the perceived health status evolution among elderly subjects and examined the age-related differences in perceived health when comparing estimates obtained from cross-sectional and longitudinal approaches. Data come from a cohort of non-institutionalized individuals aged 65 years or older, living in Barcelona, Spain. One thousand three hundred fifteen (1315) elderly were successfully interviewed at baseline in 1986 and 754 (84.6% of the eligible) at the re-assessment (1993-1994). Estimates of change in perceived health status were calculated based on cross-sectional and longitudinal approaches. Cross-sectionally, no significant differences in the proportion of individuals with poor self-rated health were found (40.5 vs. 42.5%, P = 0.90). Among survivors, the proportion of individuals with poor health increased from 37.8% to 55.1% (P < 0.01), an 8.7-fold decline of perceived health when compared with the cross-sectional estimates. Comorbidity (aOR 2.1; 95%CI: 1.4-3.3) and no education (aOR 1.9; 95%CI: 1.1-3.2) were associated with a decline in health status after adjusting by baseline health status. We recommend the use of longitudinal studies to understand the evolution of perceived health in the elderly.

The Pain and Function of the Hip (PFH) Scale: Patient-Based Instrument for Measuring Outcome After Total Hip Replacement

The Pain and Function of the Hip (PFH) scale was developed following the recommendations of the Société International de Chirurgie Orthopedique et Traumatologie to assess the outcomes of total hip replacement (THR). This study evaluated metric properties of the PFH scale and its ability to measure clinical change (responsiveness) in consecutive patients undergoing THR. Patients were evaluated preoperatively and at 3 and at 12 months postoperatively. The PFH scale and the Nottingham Health Profile (NHP) were administered. Complete data were collected for 79 patients. Mean overall preoperative PFH score was 26.5 and mean overall PFH score 12 months postoperatively was 69.8 (P < .01). Correlation with the NHP was high (r = -0.64), and the magnitude of improvement (effect size) as assessed by the PFH scale was large (3.6 compared with 1.7 for the NHP). The PFH scale is simple and valid, and may complement routine clinical evaluation of hip replacement. Residual pain after hip replacement may have been previously underestimated.