How is comorbidity affected by a double positive?
By Jason Bhan, MD, Fernando Schwartz, PhD, and Lauren Wiener>
If you read our previous blog, you know that Prognos has set out to prove that diabetes and rheumatoid arthritis are comorbid conditions. In today’s blog we are ready to share our findings with our readers.
As a reminder, we hypothesized that our analysis would point to a comorbidity between diabetes and RA, and also set out to investigate whether patients with a double positive RA diagnosis would be affected by the presence of a diabetes comorbidity. We searched the expansive Prognos Registry to find patients with diabetes and RA, as well as double positive RA patients (RF+ and anti-CCP+) and performed detailed analyses, including a chi square test, to find statistically significant differences between populations.
Study Results: Comorbidity
The Prognos Registry contains 24,252,264 patients with type 2 diabetes, and 2,114,010 patients with RA. Of these patients, 608,540 are comorbid and are diagnosed with both type 2 diabetes and RA. These results mean that 28.79% of RA patients have diabetes, which is a significant comorbidity, and is similar to the 31% reported in a research study with 340 RA patients. Our results also show that 2.51% of diabetes patients have RA, which is a striking comorbidity given that RA is absent from current standards of care guidelines for diabetes.
The Prognos database currently has a total of over 175 million patients across all conditions. Of the patients in the database, 13.799% have diabetes and 1.203% have RA. If the two diseases were independent, 0.166% of patients in the database would have diabetes and RA. However, 0.346% of patients in the Prognos database were found to have both diabetes and RA. Our findings report a comorbidity between diabetes and RA with an unprecedented sample size.
Study Results: Double Positive Risk Factor
Of the 2,114,010 RA patients, 121,546 were found to have a double positive diagnosis, and 1,992,464 were found to not have a double positive diagnosis. The distribution of the double positive patients between the just RA and comorbid population are shown in the table below:
We were surprised to find that a double positive diagnosis is more common in the population suffering solely from RA rather than the comorbid population. Both RA and diabetes are inflammatory diseases, so a double positive could be expected to be more common in a comorbid population.
Of the patients that had only RA, 5.977% had a double positive diagnosis, and 5.187% of comorbid patients had a double positive diagnosis. A chi-square test was performed, which resulted in a chi-square statistic of 499.165, a p value of 2.2e-16, and one degree of freedom. The null hypothesis for the chi-square test is that there is no difference between the two populations. This small p value means we can reject the null hypothesis. The RA-only and comorbid populations differ with respect to a double positive diagnosis with a high degree of certainty.
What’s to Come…
Next week we’ll wrap up with our thoughts on what this could all mean. As always, we encourage you to follow along with us and to reach out to us at email@example.com with questions or to request additional information.