Monday, October 24, 2011

Another Reason Why There Was A Decline In U.S. Hospitalizations for Heart Failure

By now, many Disease Management Care Blog readers have become aware of this JAMA research study that used Medicare fee-for-service claims data to examine the nationwide rate of hospitalizations for chronic heart failure.  From 1998 to 2008, there was a counterintuitive 30% decline in the U.S. from a baseline rate of 2845 to a new rate of 2007 admissions per 100,000 person-years. 

The authors credit better care of heart attacks (damage from a heart attack to can lead to a flabby dilated heart), better prevention (such as more aggressive treatment of high blood pressure, which also causes heart damage) and a more "effective" medical system (such as better outpatient follow-up, use of alternate levels of care, flu shots prescriptions of ACE inhibitors and beta blocker medications).  The authors of the study think the numbers are remarkable because the U.S. population is getting older and healthier persons (without heart failure) seem to be signing up for managed care Medicare Advantage.

The DMCB is wondering about another possibility that has nothing to do with epidemiology or quality.  Rather, it could be the impact of Medicare payment rates on billing patterns.  After all, if heart failure is the leading Medicare inpatient diagnosis, shouldn't a decrease there have an impact on the overall hospitalization rate?

The DMCB explains:

When beneficiaries are discharged from a hospital, the bill (or the claim) submitted to Medicare is based on a "Diagnosis Related Group."  While the invention and logic of DRGs complicated, they're important because the principal diagnosis determines the amount of the global payment for that hospitalization. While this may be overly simplistic, a discharge with a diagnosis of "heart failure" prompts Medicare to pay a hospital "X" dollars, while a diagnosis of pneumonia or kidney failure will render payments of "Y" and "Z" dollars, respectively.  In general, the more complicated the diagnosis, the greater the payment.

All well and good, but suppose the hospital has a patient with several concurrent problems and has a choice on which DRG to use?  As anyone who has taken care of hospitalized patients knows, there are usually multiple diagnoses present in any patient at one time.  Pneumonia may or may not have provoked the heart attack that led to the kidney failure that led to the leg swelling and the shortness of breath.  Given three simultaneous diagnoses, Medicare billing guidelines state that the hospital should use their best judgement to determine which DRG to bill. All things being equal, smart hospitals will probably use the DRG that renders the greatest payment.

The DMCB isn't saying that fraudulent billing (for example) accounts for the decrease in heart failure hospitalizations for Medicare. However, it knows some diagnosis related groups can be less remunerative than others and that in the last ten years, DRG payment rates have evolved and that hospitals have learned how to "code" more accurately and aggressively.  Based on the example at the bottom of this page, the DMCB wonders if some patients that were diagnosed with heart failure in 1988 would have been diagnosed with something more remunerative in 2007. 

In other words, there may have been the same number of hospitalizations involving the same patients with the same disease burden.  It was the case mix that changed?

The authors of the study to their credit can't discount the possibility:  They argue that if coding had changed there would have been a shift in the mortality rate of patients with heart failure:

"We were unable to determine whether the observed changes were due to changes by hospitals in medical coding; however, substantial up-coding or down-coding would likely result in changes to the coefficients of the CMS HF mortality model, and these coefficients remained stable from 2005 to 2008."

The authors may have a point, but that assumes the modeling - also based on claims - is trustworthy.

Of course, there is no way, based on Medicare billing claims alone, to determine whether measurement also played a role in the decline in heart failure admissions.  That would take an audit of the medical records themselves.

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