Had a Nuss of this?

Nuss Principal Procedure (ICD-10-PCS 0PS0447)

Editor’s Note: This article was originally published in the American College of Physician Advisors Newsletter.

How many times have you had a provider immediately respond, “the coding must be wrong,” when you engaged in a quality discussion? And, after you went in circles (and took several detours) explaining the documentation, the coding, and the metric’s definition, how much time was actually left to talk about bedside patient safety?

Providers’ default of disbelief is often anchored by suspicion in how the ‘data’ is derived – the inclusion and exclusion criteria seemingly live behind a curtain few peek behind, and even fewer completely understand. But the details matter, because they populate the dashboards and scorecards most providers receive. In this article, a Clinical Quality Specialist nurse threw open the curtain, helped shine some light on a previously unidentified misrepresentation of quality, and sparked change in an AHRQ metric on a national level.

In 2018 CMS reassigned the Major Diagnostic Category (MDC) for congenital pectus excavatum (ICD-10-CM Q67.6) from MDC 4 (Respiratory Conditions) to MDC 8 (Musculoskeletal and Connective Tissue Conditions) after receiving a request to align the MDCs of the corrective “Nuss” procedure (ICD-10-PCS 0PS0447, MDC 8) with the underlying medical conditions (ICD-10-CM Q67.6 “congenital pectus excavatum”, originally MDC 4; ICD-10-CM M95.4 “acquired pectus excavatum”, originally MDC 8).

By aligning all of the ICD-10-CM and ICD-10-PCS codes to MDC 8, there was a subsequent MS-DRG shift from 981-983 (Procedure Unrelated to Principal Diagnosis) to 515-517 (Other Musculoskeletal System and Connective Tissue O.R. procedures with MCC, with CC, and without CC/MCC, respectively) based on coding logic. This occurred because BOTH the medical and procedural Principal Diagnoses fell within the same MDC (08), which had NOT been true prior to CMS’s 2018 reassignment1.

At the University of Colorado Hospital, patients are regionally referred for the corrective “Nuss” procedure by a highly specialized Cardiothoracic Surgeon. For a Nuss procedure to correct pectus excavatum, there is deliberate entry into the pleural space as a planned aspect of the procedure. Post-operative pneumothoraces and chest-tubes are not infrequently part of the post-op course.

In 2020, the hospital’s Vizient Comprehensive Academic Medical Center Quality and Accountability Performance Scorecard demonstrated down trending from the year prior, and members of the Quality Department were asked to investigate. A review indicated that the primary area of opportunity was in “Safety,” which comprises 25% of the score. The Safety domain includes Patient Safety Indicators (PSIs) developed by the Agency for Healthcare and Research and Quality (AHRQ), NHSN Infection Surveillance and Laboratory ID Metrics, and the total hip and knee (THK) complication rate measure. The Clinical Quality Specialist (CQS) nurse identified PSI-06 Iatrogenic Pneumothorax metric performance (Z-Score) as specifically having undergone a significant negative change.

What the CQS learned about PSI-06 (Iatrogenic Pneumothorax) was that the relative rate per 1000 cases was quite low; which meant that a difference of just a few complications drastically affected the Z-Score, for better or worse. The CQS took a deep dive, performing chart reviews of each identified case, utilizing the AHRQ PSI Toolkit2. What was uncovered did not initially seem to make any sense: patients undergoing the Nuss surgery were showing up on the list. Review of the coding revealed a MS-DRG within the musculoskeletal and connective tissue MDC, instead of respiratory/thoracic.

Why would a surgery which is definitively a thoracic case – entering the chest cavity as part-and-parcel of the procedure3 – code to MSK/Connective Tissue? How could it not meet exclusion criteria for the PSI-06 metric?

The hunt began, to answer these questions. Through asking the ‘how’ and the ‘why’, the CQS assembled a multidisciplinary team including a Cardiothoracic Surgery physician partner, Surgical service-line leadership, Quality, Clinical Documentation Integrity, and Coding. The team analyzed the Coding (which was correct), reviewed the Documentation (which was accurate, albeit did not specifically describe the clinical significance of the pneumothoraces, when present), and assessed the clinical Utilization of resources (which were appropriate for the clinical condition). What was learned: a Nuss Principal Procedure (ICD-10-PCS 0PS0447) did not meet PSI-06 exclusion criteria because it was considered a corrective procedure for Diseases and Disorders of the Musculoskeletal System and Connective Tissue (ICD-10-CM Q67.6, MDC 8) and not a MDC 4 (Diseases and Disorders of the Respiratory System).

The team elicited that the 2018 CMS MDC code reassignment – while well-intentioned to align both the medical condition and surgical correction within the same MDC – had placed them within a MDC (08) which would not meet exclusion criteria for PSI-06 (such as surgical codes within MDC 4).

The following potential solutions were considered:

(1) Uniformly define pneumothorax as intrinsic to the procedure. This would prevent the need to code J95.811 and therefore not trigger PSI-06. The CDI Physician Advisor noted both the risk that documentation may not always indicate the integral relationship and the risk of under-documenting/under-coding clinically significant and/or unrelated pneumothoraces.

(2) Adopt post-operative clinical pathways to reduce potential overutilization of imaging (sp. CXR) which may incidentally diagnose clinically insignificant pneumothoraces. While the Cardiothoracic Surgeon supported limiting imaging to medically necessary situations, risk of under-recognition and potential clinical harm was identified.

(3) Advocate to CMS code reassignment for BOTH the relevant ICD-10-CM and ICD-10-PCS into MDC 4 (Respiratory Conditions), which would also have a subsequent MS-DRG change. The CDI and Coding Physician Advisors noted the recent, aforementioned code reassignment from 2018 and recognized that down-stream impact on complication metrics would likely be insufficient clinical basis upon which to request a national coding change, particularly with the fairly recent change placing both into MDC 4.

(4) Advocate to AHRQ the clinical basis for placing the Nuss procedure on the list of PSI-06 exclusion criteria, for the same reason all other thoracic surgeries are excluded.

There are often numerous methods of tackling issues straddling as many realms as this one did. Sometimes, the easiest solution is the right one. Including robust description of the operative procedure by the Cardiothoracic Surgeon, this team chose (4) and presented the position to the AHRQ QI Technical Support Team.

The request was well received: “AHRQ understands that this procedure by definition includes thoracoscopy, pleural cavity entry, and insufflation of the pleural space. Accordingly, AHRQ is adding 0PS044Z and a substantial number of similar 0P codes involving open and thoracoscopic approaches to the THORAIP list, which will exclude these records from the denominator of PSI 06 in the v2021 software release.”

Bringing this full circle, was the coding wrong? No. Was documentation lacking? Not really. Were the metrics flawed? Well, since they followed the coding logic consistent with the reassignments made in 2018 and effectively identified secondary diagnosis codes not on the Denominator Exclusion list, the answer is debatably no. The provider’s predilection to instinctively disbelieve what the original data said about their Quality of care proved true – because metrics, like people, are imperfect and available for improvement. But after involving the provider in the process and empowering them to assert the clinical basis of a solution3, do you think they are more or less likely to trust that their voice will be heard the next time we call on them for quality improvement?


Programming Note:  Listen to Drs. Drew Updike and Debra Anoff report this story live today as special guests during Talk Ten Tuesdays, 10-10:30 a.m. Eastern.


1. https://www.regulations.gov/document?D=CMS-2018-0046-1659  

2. https://www.ahrq.gov/patient-safety/settings/hospital/resource/qitool/index.html

3. Nuss et al. Ann Cardiothorac Surg 2016;5(5):422-433.

Clinical Quality Specialist in the Department of Clinical Quality and Patient Safety

University of Colorado Hospital in Aurora, CO

LinkedIn: Alyson Dare Kelleher

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