OBJECTIVES: Patients with hip or knee osteoarthritis (OA) may experience functional limitations in work settings. In the Cohort Hip and Cohort Knee study (CHECK) physical function was both self-reported and measured performance-based, using Functional Capacity Evaluation (FCE). Relations between self-reported scores on SF-36 and WOMAC (Western Ontario and McMaster Arthritis Index, function scales) and FCE performance were studied, and their diagnostic value for clinicians in predicting observed physical work limitations was assessed.METHODS: Ninety-two subjects scored physical function on SF-36 (scale 0-100, 100 indicating the best health level) and WOMAC (scale 0-68, 68 indicates maximum restriction) and performed the FCE. Correlations were calculated between all scores. Cross-tables were constructed using both questionnaires as diagnostic tests to identify work limitations. Subjects lifting <22.5 kg on the FCE-test 'lifting-low' were labeled as having physical work limitations. Diagnostic aspects at different cut-off scores for both questionnaires were analysed.RESULTS: Statistically significant correlations (Spearman's rho 0.34-0.49) were found between questionnaire scores and lifting and carrying tests. Results of a diagnostic cross-table with cut-off point <60 on SF-36 'physical functioning' were: sensitivity 0.34, specificity 0.97 and positive predictive value (PV+) 0.95. Cut-off point > or =21 on WOMAC 'function' resulted in sensitivity 0.51, specificity 0.88 and PV+ 0.88.CONCLUSION: Low self-reported function scores on SF-36 and WOMAC diagnosed subjects with limitations on the FCE. However, high scores did not guarantee performance without physical work limitations. These results are specific to the tested persons with early OA, in populations with a different prevalence of limitations, different diagnostic values will be found. FCE may be indicated to help clinicians to assess actual work capacity.
Purpose: The etiology of pain in osteoarthritis (OA) is complex andmultifactorial. A growing number of studies suggest that modificationof pain-transmission in the peripheral and central nervous system,leading to sensitization, plays a role in OA pain. Sensitization seems tobe associated with neuropathic pain-like symptoms and assessment ofthese symptoms can help to identify patients who could benefit fromadditional treatment options. Several questionnaires are available todistinguish neuropathic from nociceptive pain symptoms. The modifiedpainDETECT questionnaire (mPDQ) is a self-reported questionnairedeveloped to discriminate between nociceptive- and possible/likelyneuropathic pain in knee OA patients. Recently the mPDQ was translatedinto Dutch and adjusted to also fit hip OA patients. The aim of thisstudy was to assess the validity of the mPDQ-NL in patients with hip orknee OA.Methods: Primary hip and knee OA patients were recruited from threeDutch hospitals. Based on previous research, confirmatory factor analysisfor two principal components was performed to assess structuralvalidity. Construct validity (both convergent and divergent) wasassessed using hypothesis testing. Predefined hypotheses were formulatedconcerning the correlation between the mPDQ-NL and theSelf-reported Leeds Assessment of Neuropathic Symptoms and Signs (SLANSS),subscales of the Knee injury and Osteoarthritis Outcome score/Hip disability and Osteoarthritis Outcome Score (KOOS/HOOS), VisualAnalogue Scale for pain (VAS pain), and subscales of the RAND-36health survey (RAND-36). According to the COSMIN criteria, constructvalidity of a questionnaire is sufficient if 75% of predefined hypothesesare met. Additionally, convergent validity was assessed with blunt PainPressure Thresholds (PPTs) in a subsample of participants. A reducedPPT is a somatosensory abnormality that is considered an indication ofsensitization in OA. Therefore it was expected that reduction of PPTswas associated with higher mPDQ scores.Results: 168 participants were included. PPT measurements wereperformed in a sample of 46 participants. Factor analysis confirmed twoprincipal components. The items that loaded on the first componentcould be described as “evoked neuropathic sensations”, the items thatloaded on the second component as “spontaneous neuropathic sensations”.However there were two items that substantially loaded on bothcomponents. The item regarding pain pattern did not load on anycomponent. Considering construct analysis, 80% of the predefinedhypotheses concerning the correlation between mPDQ and self-reportedquestionnaires were met. Considering the correlation with PPTmeasurements, 50% of the predefined hypotheses were met.Conclusions: The mPDQ-NL seems to adequately reflect neuropathicpain-like symptoms experienced by hip and knee OA patients. Concerningstructural validity, two determinative components seem to bepresent, in line with previous research. However, one particular itemregarding pain pattern might not reflect the construct of neuropathicpain-like symptoms in hip or knee OA. Therefore, when using the mPDQin hip or knee OA patients, it might be considered to skip this particularitem. Construct validity can be considered sufficient, with over 75% ofthe predefined hypotheses regarding correlation between the mPDQNLand other questionnaires were met. However, only 50% of the hypotheses concerning PPT measurements were met, probably due toheterogeneity and limited sample size of this subgroup. To ourknowledge, this study is the first to assess the structural validity of themPDQ knee and hip by using factor analysis and to assess constructvalidity using elaborate hypothesis testing as proposed by the COSMINguidelines.
Background: The modified painDETECT questionnaire (PDQ) is a self-reported questionnaire to discriminatebetween nociceptive and neuropathic-like pain in patients with knee/hip osteoarthritis (OA). This studyaims to assess the structural and construct validity of this questionnaire.Methods: Confirmatory factor analysis and hypothesis-testing was used. For 168 patients, predefinedhypotheses were formulated on the correlation between the modified painDETECT and several otherquestionnaires, and in a subsample of 46 with pain pressure thresholds (PPTs).Results: Two principal components were confirmed. The pain pattern item did not load on any component.Eighty per cent of the hypotheses on the correlation between modified PDQ and the questionnaireswere met, as were 50% concerning PPTs measurements.Conclusions: This study is the first to assess structural and construct validity of the modified PDQ knee/hip by using factor analysis and hypothesis-testing. This questionnaire seems to reflect neuropathic-like pain symptoms experienced by hip/knee OA-patients with adequate validity. The item on pain patternmight not reflect the construct. More than 75% of the predefined hypotheses regarding the modified PDQ and the other questionnaires were met. Only 50% of the hypotheses on PPTs measurements were met, probably due to heterogeneity and limited size of this subsample.
