Our Medicare Part A claim was rejected due to “principal diagnosis is an unacceptable diagnosis. Correct and resubmit/rekey”. The principal diagnosis coded on the Medicare claim and in section I0020B of the Medicare 5-day MDS is B95.62 (MRSA infection as the cause of diseases classified elsewhere). For PDPM, this code is not a return to provider (RTP) code and it clinically maps to the acute infection’s clinical category. I am not sure what the issue is or how to resolve it so the Medicare claim for this patient will process and pay.


When coding diagnoses, it is important to be mindful of the ICD-10 Coding Guidelines and validate not just that the code is an acceptable diagnosis in the clinical mapping for PDPM, but to also follow the Official Coding Guidelines for Coding and Reporting Diagnosis Codes.

CMS uses Medicare Code Edits (MCE) to validate that the claim is properly coded to avoid inappropriate payment on inpatient claims. These edits previously applied only to acute hospital inpatient claims, but the system has been updated to include SNF Part A claims billed to Medicare.

Below is a link to the diagnoses that are unacceptable as primary:


Many of the codes are B codes used to identify the infectious agent for an infection like the one in your question.  In this case since the descriptor of the code indicates it is the cause of diseases classified elsewhere there must be an additional code on the claim to identify this disease. For example, when the patient has a urinary tract infection (UTI) due to MRSA – codes include N39.0 and B95.62.  In the absence of the additional diagnosis to identify the type of infection the claim will reject. This claim should be corrected and then resubmitted for payment. In the example above the N39.0 code for the UTI should be first listed as principal followed by the B95.62


The rejected claim should be re-coded with the appropriate diagnosis codes and resubmitted for payment once the correction has been completed.


Christine Twombly RN-BC, RAC-MT, RAC-MTA, HCRM, CHC
Clinical Consultant

Click here to learn more about the rest of the Proactive team.