We are a critical access hospital with a psychiatric unit that bills under POS code 21 but are excluded from the IPPS. Should these patients be included in the denominator for the Meaningful Use measures?

No. According to the final rule, the definition of hospital used for Meaningful Use measures does not apply to hospitals excluded from the inpatient prospective payment system (IPPS), such as psychiatric or rehabilitation units. If patients treated in the psychiatric unit are also admitted to areas of the inpatient department that are not excluded from IPPS, then they should be counted in the denominator (and numerator) for Meaningful Use measures.

For more information, see the CMS FAQ on this topic.