Abstract
Objective Many patients have medically unexplained physical symptoms (MUPS); some of them attribute their health complaints to dental amalgam fillings. The aim of this study was to assess the validity and responsiveness of General Health Complaints index (GHC-index) for measuring the symptom load in MUPS patients compared to the widely used symptom outcome measure, Giessen Subjective Complaints List (GBB-24). Methods Three outcome measures – GHC-index, GBB-24, and Munich Amalgam Scale (MAS) – were administered at baseline and 12 months after removal of all dental amalgam restorations. The validity and responsiveness of these symptom measures were tested against external anchors: bodily distress syndrome (BDS), SF-36 vitality, and visual analogue scale (VAS). We tested both convergent and known group validities. We also examined the predictive validity and responsiveness to changes for each instrument. Results All the main outcome measures showed evidence of convergent and known group validities. The GHC-index, GBB-24 and MAS were all able to detect the anticipated differences in BDS and Energy. But the GBB-24 was more efficient in discriminating the BDS compared with the GHC-index (relative efficiency: RE = 0.69; 95% CI: 0.41–0.96) and MAS (RE = 0.59; 95% CI: 0.32–0.86). Each main outcome variable revealed good predictive validity for vitality (standardized coefficient: b ≈ 0.71 and R 2 ≈ 0.50). Moderate to high sensitivity to change over time was demonstrated, with GHC-index performing better. Conclusion The GHC-index is a valid and responsive instrument for assessing symptom load in MUPS patients attributing their health complaints to amalgam fillings and undergoing amalgam removal.
Highlights
Patients with medically unexplained physical symptoms (MUPS) suffer from persistent health complaints that cannot be sufficiently explained by observable physical pathology despite intensive diagnostic efforts [1,2]
Exceptions were for baseline observations between visual analogue scale (VAS) and Munich Amalgam Scale (MAS) and between Vitality and MAS, where moderate convergent validity was found
The percentages of participants with meaningful changes in either direction for each outcome measure varied between 43.8% and 56.3%, with the GHC-index performing slightly better than both MAS and GBB-24. This analysis contributes to the knowledge of the psychometric properties of questionnaires used to measure symptom load in MUPS patients
Summary
Patients with medically unexplained physical symptoms (MUPS) suffer from persistent health complaints that cannot be sufficiently explained by observable physical pathology despite intensive diagnostic efforts [1,2]. Studies suggest between 3% and 50% of primary care patients present with MUPS [3,4,5,6]. Such variations in the prevalence of MUPS could be due to differences in the diagnostic criteria [3]. Evidence suggests that MUPS exists on a continuum of severity, ranging from patients with transient, mild symptoms to those with multiple, debilitating unexplained symptoms [7,8], constituting a major burden with considerable societal costs of direct healthcare or lost productivity. The costs attributable to MUPS due to lost productivity alone is over £5 billion per annum to the UK economy [10], and e7645 per patient per 6-month in Germany [11]
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