The definition of N_HOSP_U differs by HCUP database:

• For the NIS prior to 2012, N_HOSP_U contains the total number of hospitals in the universe of AHA community excluding non-rehabilitation hospitals for the stratum.
• For the NIS beginning in 2012, N_HOSP_U contains the total number of hospitals in the universe of AHA community excluding non-rehabilitation and long-term acute care (LTAC) hospitals for the stratum.
• For the NRD, N_HOSP_U contains the total number of hospitals in the universe of AHA community excluding non-rehabilitation and LTAC hospitals for the stratum.
• For the NEDS, N_HOSP_U contains the total number of EDs in the universe of AHA hospital-based emergency departments for the stratum.
• For the NASS, N_HOSP_U contains the total number of community (general medical/surgical and childrens) hospitals performing major ambulatory surgeries for the stratum.