True Difference or Something Else? Problems in Cost of Osteoarthritis Studies

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Objectives

To identify the commonalities and discrepancies among the published cost of osteoarthritis (OA) studies and to further propose some potential improvements for this type of research.

Methods

A systematic literature review was performed on MEDLINE (1966 to April 2006) by using 2 overlapping search strategies to identify cost of illness studies in OA based on the predefined eligible criteria. Direct and indirect costs per patient per annum were separately summarized across studies and countries. The sample size-weighted mean was calculated when there were 2 or more studies from the same country. Discount rates of 3% and appropriate exchange rates were used in conversion of the costs reported in different years and different currencies to 2005 US dollars.

Results

Ten articles fulfilling the eligible criteria were included in the literature synthesis. Of these, 4 were from the USA, 2 each from Canada and France, and 1 each from Italy and Hong Kong. After adjusted to 2005 US dollars, annual direct costs per patient (in descending order) were $9147 in Hong Kong, $4792 in USA, $2878 in Canada, $1271 in Italy, and $345 in France. In contrast, indirect costs were only reported by 5 studies in 4 countries. The highest indirect costs were $9847 per patient per annum in Canada and the lowest were $864 in Hong Kong.

Conclusions

The observed substantial variations in costs of OA across studies and countries may not reflect the true differences among them. The comparability across these identified studies is quite limited, which highlights the importance of standardization in cost of OA studies.

Section snippets

Literature Search Strategy

A systematic literature review was performed on MEDLINE (1966 to April 2006). To identify as many potentially relevant articles as possible from the literature, 2 overlapping strategies were adopted in the literature search as recommended by Petitti (15). The first strategy used “osteoarthritis” combined with “economic burden,” “direct costs,” “indirect costs,” “expenditures,” and “cost-of-illness” as text words. The second strategy used “osteoarthritis” combined with “costs” as title words to

Identification of Potentially Relevant Articles

As shown in Fig. 1, the electronic search of MEDLINE yielded a total of 224 articles. After checking for duplication, a total of 142 articles were identified for title and abstract scan. Of these, 127 were obviously irrelevant and excluded from further review. The full texts of the remaining 15 articles were reviewed. Of 15 articles, 1 duplicating the results that were already included and 4 that did not report direct or indirect costs of OA were excluded. No relevant article was identified

Discussion

This systematic review identified only 10 articles estimating the direct costs of OA per patient per annum, only 5 of which reported the indirect costs per patient per annum simultaneously. To the best of our knowledge, the present study may be the first systematic literature review on the cost of OA studies in the past decade. Several findings need to be highlighted. First, cost of OA studies were insufficiently performed in the past decade, especially in developing countries. Second, the

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    There has been no funding or any other support received in support of this study, and none of the authors has any financial interest relating to the article that might constitute a potential conflict of interest.

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