This population-based study estimates the impact of CD diagnosis on direct medical costs of care as well as the incremental costs associated with CD prior to diagnosis. Even with the exclusion of costs related to the diagnostic process, we find that direct medical outpatient and total costs were significantly reduced for patients in the year following CD diagnosis. Furthermore, CD patients experienced significantly higher direct medical costs during the 4-year observation period (nearly $4,000, on average) compared with unaffected peers, suggesting a substantial economic burden of disease.
These results are consistent with those recently published by Green et al. (2008), who used outpatient administrative claims data to assess the economic implications of CD diagnosis (15
). A particular strength of our study was our ability to link detailed medical records data (including laboratory data) to line item utilization and cost data regardless of payer type. In our population-based design, the diagnosis of CD was confirmed by re-review of the medical record and was not only based on diagnostic codes. Thus, this study design decreased bias induced by referral, missing data, and inaccurate coding. Our results suggest a 29% reduction in outpatient costs in the year following diagnosis as well as an overall 39% reduction in total medical cost of care. Our decision to limit costs that relate to the diagnosis of CD to 90 days for tests and 15 days for office visits is consistent with our experience in a major tertiary referral center with expertise in CD but may be too restrictive in other settings or populations.
To our knowledge, we are the first study to assess incremental costs attributable to CD despite the fact that cost-of-illness studies are increasingly needed for modeling the cost-effectiveness of alternative treatments and for informing clinical and public health policy (27
). In our sample, undiagnosed and untreated CD patients incurred nearly $4,000 in excess 4-year medical costs compared with non-CD matched peers. This significant economic burden was even more pronounced among males with CD, who incurred over $10,000 more, on average, in medical costs during the study period than their matched non-diseased controls. The reasons for this finding are not totally clear, but clinically-detected CD is twice as frequent among women as men and it is possible that male symptoms could more often be attributed to different causes other than CD (such as irritable bowl syndrome), increasing both the number of clinic visits to make the correct diagnosis and the cost of care (1
). Sex-related differences in both clinical presentation of CD and comorbidity may also affect estimates of cost of care, including prior evidence of more severe disease in males (31
Our post hoc analyses of incremental costs between CD cases and controls stratified by severity and clinical presentation suggest that the excess total costs associated with CD we observed are largely driven by significant excess outpatient costs in patients with classical CD (characterized by a diarrhea-predominant syndrome) and in patients with non-severe CD (defined by the absence of a combination of diarrhea and weight loss). Reasons to explain these differences are unknown but we can speculate it may be related to a more extensive differential diagnosis in non-severe CD, expedited diagnosis of severe cases, cost inherent to the approach of undiagnosed chronic diarrhea, and serology-driven diagnosis of atypical cases. Further studies to address these hypotheses are not only necessary but are clinically relevant.
Although not statistically significant, we also found it curious that inpatient costs were observed to be over $2,400 higher (p=0.11), on average, for CD patients in our sample compared with controls since anecdotally CD does not seem to be a condition with an acute need for inpatient care. To investigate this further, we performed additional subgroup analyses stratifying by whether inpatient events were considered CD-related or not based on a blinded clinical review of primary discharge diagnoses. Examples of episodes considered CD-related include a diagnosis of anemia, unspecified constipation, generalized abdominal pain, and intussusception. Interestingly, inpatient costs for CD-related episodes were significantly higher, on average, for CD cases than controls ($392 vs. $33; p=0.05). Costs for non-CD inpatient episodes were also observed to be $1,565 higher, on average, for CD cases compared with controls, but this difference was not statistically significant. Thus, at least some of the higher inpatients cost in CD cases are explained by higher CD-related inpatient episodes.
Our study also has potential limitations to note. The present study was conducted in a single geographic setting, Olmsted County, where the population is predominately of white ethnicity and much of the care obtained by study participants occurred at a high volume referral center (16
). Patients and results may differ in other practice settings and locales. We also acknowledge our relatively small sample sizes, particularly in stratified analyses, hindering cost comparisons given the high variability and skewed nature of this outcome. Furthermore, while we did restrict our sample to individuals with verified county residency to limit missing data concerns, the possibility still remains that some individuals may have obtained healthcare outside our local setting. Finally, a significant limitation of this study design is that our analysis was focused on costs from the health care provider perspective, and it does not include pharmaceutical costs, decreased work productivity, or the very significant out-of-pocket cost associated with gluten-free food that can be 2–4 times as expensive as its wheat-based foods (13
). It remains possible that our observed reduction in medical cost after CD diagnosis and treatment may have shifted the economic burden to patients as the excess cost associated with the gluten-free diet is not reimbursed by payers in the U.S unlike in other countries such as Finland where a monthly compensation (“dietary grant”) has been paid by a Social Insurance Institution since 2002 (33
). Finally, quality of life implications associated with a gluten-free diet or CD that may be of significant concern from a patient perspective were not analyzed (34
In conclusion, using a population-based study design, our estimates of CD-associated costs indicate a significant economic burden of disease, particularly for men with CD. Diagnosis and treatment of CD significantly reduces direct medical costs of care, suggesting an economic advantage to earlier detection and treatment.