Pseudogout among Patients Fulfilling a Billing Code Algorithm for Calcium Pyrophosphate Deposition Disease

Area of Science:

• Rheumatology
• Medical Informatics

Background:

• Calcium pyrophosphate deposition disease (CPPD) is a crystal-induced arthropathy.
• Accurate identification of pseudogout cases is crucial for epidemiological studies and clinical research.
• Existing billing code-based algorithms for CPPD may have limitations in accurately capturing pseudogout diagnoses.

Purpose of the Study:

• To evaluate the performance of a published billing claims-based algorithm for identifying pseudogout.
• To assess the impact of incorporating automated text searching of clinical notes on the algorithm's accuracy.
• To determine the prevalence of pseudogout among patients not identified by the algorithm.

Main Methods:

• A published CPPD algorithm was applied to billing claims data at an academic institution.
• 100 patients were randomly selected for electronic medical record review to assess diagnostic phenotypes.
• The algorithm was modified to include text-based searches for specific terms in clinical notes, and positive predictive values (PPVs) were recalculated.
• A separate sample of 50 patients not meeting the original algorithm criteria underwent review to estimate missed cases.

Main Results:

• The original algorithm demonstrated low positive predictive values (PPVs) for definite/probable pseudogout (24.0%) and definite pseudogout (18.0%).
• Modifying the algorithm to include text searches for relevant terms increased PPVs to 33.3% for definite/probable pseudogout and 24.6% for definite pseudogout.
• A significant proportion of patients (16.0% definite/probable, 6.0% definite) with pseudogout were not identified by the original algorithm.
• Even with text searching, the overall PPV for pseudogout identification remained suboptimal.

Conclusions:

• Billing code-based algorithms alone have limited accuracy for identifying pseudogout.
• Integrating automated text searching in clinical notes offers a modest improvement in identifying pseudogout cases.
• More robust methods are needed to enhance the accurate identification of pseudogout for research purposes.