The medical billing profession is not without its struggles, and nowhere is this more apparent than in hospitals. With so many patients coming and going on a constant basis, it can be hard to check every last claim, which in turn can lead to a number of billing errors. The Office of Inspector General (OIG) recently conducted an audit of a major Chicago hospital, analyzing 120 randomly selected claims in order to check them for compliance. Startlingly, 57 of these claims were found to have errors which cumulatively resulted in roughly $814,000 worth of overpayment during the 2014-2015 audit period.

In particular, OIG pinpointed a few areas that contained the highest levels of risk and, by extension, the most billing errors. One of these was the diagnosis related group (DRG); five of the audited claims had an incorrect DRG code. Close behind with four instances of error were claims that were not supported by proper medical necessity.

Though only accounting for two of the billing errors, incorrect use of modifier 59 was still a prevalent problem. Though meant to be used for a distinct procedural service (such as a different procedure, a different body system being treated, or a different encounter altogether), this code was sometimes appended to procedure codes that already included the service in question.

By far the biggest sources of billing errors, however, were the services billed in inpatient rehabilitation facilities (IRFs). These facilities are reserved for patients with complex issues that “can reasonably be expected to benefit from an inpatient stay and an interdisciplinary team approach to the delivery of rehabilitation care.” But in a staggering 46 of the total reviewed claims, patients staying in the IRF did not meet the Medicare standards for that level of care.

Though this audit only reviewed one hospital, their findings suggest that many others may have the same issues. If you work for a major facility, take the time to review your claims to ensure that these same sorts of billing errors don’t slip through the cracks.