On October 9, 2013, the OIG released a report focused on questionable Medicare billing for polysomnography services in 2011. Polysomnography is a type of sleep study that has seen increasing Medicare spending over the past few years and that the OIG notes has been identified as being vulnerable to fraud and abuse. The report analyzed polysomnography claims submitted by both hospital outpatient departments and nonhospital providers such as independent diagnostic testing facilities and physician-owned sleep laboratories. The OIG identified claims amounting to $16.8 million that did not meet Medicare requirements, many of which were due to inappropriate diagnosis codes submitted by hospital outpatient departments. In addition, the report found that 180 providers exhibited patterns of what the OIG identified as questionable billing, the majority of which had unusually high rates of multiple claims for polysomnography services for the same beneficiary on the same day. Other patterns suggesting questionable billing included providers sharing the same beneficiaries (which may indicate that providers are using compromised beneficiary numbers for fraudulent billing), potential unbundling of split-night services, and cases lacking evidence of a patient relationship with the ordering provider in the preceding year. The report recommended that CMS: develop more effective claims processing edits (especially prepayment edits to ensure the appropriate use of diagnosis codes); further investigate and attempt to recover payments for claims that failed to meet Medicare requirements; consider using factors identified in the study to screen polysomnography providers in the future; refer providers with patterns of questionable billing to Medicare contractors for further investigation. CMS agreed with all four recommendations.  In addition to this study, the OIG notes that it is also conducting audits of polysomnography claims for selected regions to determine whether claims were appropriate and paid accurately.