Problems with Sensitivity, Accuracy and Bias of the Z51.5 Code as an Indicator of Specialist Palliative Care

Key Message : Among >100,000 acute hospital encounters for seriously ill patients, the Z51.5 billing code as an indicator of palliative care consultation missed nearly one-half of such encounters and was highly biased towards death or hospice. Researchers and hospitals should not rely on the billing code Z51.5 to indicate palliative care consultation.

Abstract:

Background: More than 130 studies have relied on the ICD-9/10 code V66.7/Z51.5 for “encounter for palliative care” to identify inpatient specialty palliative care (SPC) use. One validation study among adults in an urban academic center[1] and one in a pediatric population[2] have each demonstrated poor sensitivity and inaccuracy of hospital billing codes for this purpose, but the generalizability of these findings is unknown.

Objective: Examine the performance of the Z51.5 hospital billing code for SPC use in diverse U.S. hospitals alone and when combined with provider billing data and identify potential sources of bias.

Methods: We conducted a retrospective cohort study at 1 safety-net hospital in an academic medical center (2016 – 2023) and 11 community hospitals in a national health system (2016-2018). Electronic health record and administrative data were collected for acute hospital encounters among seriously ill adults. True SPC use was defined as a completed SPC consult order in the EHR, being admitted to the PCU, or presence of an SPC provider invoice.

Results: Among 115,081 hospital encounters of seriously ill patients, the overall sensitivity and positive predictive value (PPV) of the Z51.5 code for any SPC use were 57.2% and 73.1%, respectively. Sensitivity increased to 91.7% for PCU encounters, 79.3% among decedents, and 83.2% for those discharged to hospice, while it was only 45.7% for those with SPC consultation alone. Performance of the Z51.5 code modestly improved when hospital and provider billing data were combined (sensitivity 70.9%, PPV 76.9%).

Conclusion: The Z51.5 billing code fails to capture 1 in 4 instances of inpatient SPC consultation and is highly biased towards end-of-life care. Use of ICD codes risks SPC misclassification in research studies and quality improvement initiatives that can lead to erroneous interpretation of evidence with widespread impact on future research and health system decisions regarding SPC use.

References: [1] Hua M, Li G, Clancy C, Morrison RS, Wunsch H. Validation of the V66.7 Code for Palliative Care Consultation in a Single Academic Medical Center. J Palliat Med. 2017 Apr;20(4):372–7.

[2] O’Keefe S, Czaja AS. Validation of Administrative Codes for Palliative Care Consultation Among Critically Ill Children. Hosp Pediatr. 2021 Feb;11(2):179–82.