The Michigan Risk Score to predict peripherally inserted central catheter‐associated thrombosis

Unlabelled Box •How best to quantify thrombosis risk with peripherally inserted central catheters (PICC) is unknown. •Data from a registry were used to develop the Michigan Risk Score (MRS) for PICC thrombosis. •Five risk factors were associated with PICC thrombosis and used to develop a risk score. •MRS was predictive of the risk of PICC thrombosis and can be useful in clinical practice. Support for HMS is provided by Blue Cross and Blue Shield of Michigan and the Blue Care Network as part of the BCBSM Value Partnerships program. Although Blue Cross Blue Shield of Michigan and HMS work collaboratively, the opinions, beliefs and viewpoints expressed by the authors do not necessarily reflect the opinions, beliefs and viewpoints of BCBSM or any of its employees. Blue Cross/Blue Shield of Michigan and the Blue Care Network supported data collection at each participating site and funded the data‐coordinating center but had no role in study concept, interpretation of findings, or in the preparation of, final approval of or decision to submit the manuscript. V. Chopra is supported by a career development award from AHRQ (1‐K08HS022835‐01). Blue Cross and Blue Shield of Michigan and the Blue Care Network AHRQ1‐K08HS022835‐01 Summary: Background Peripherally inserted central catheters (PICCs) are associated with upper extremity deep vein thrombosis (DVT). We developed a score to predict risk of PICC‐related thrombosis. Methods Using data from the Michigan Hospital Medicine Safety Consortium, image‐confirmed upper‐extremity DVT cases were identified. A logistic, mixed‐effects model with hospital‐specific random intercepts was used to identify factors associated with PICC‐DVT. Points were assigned to each predictor, stratifying patients into four classes of risk. Internal validation was performed by bootstrapping with assessment of calibration and discrimination of the model. Results Of 23 010 patients who received PICCs, 475 (2.1%) developed symptomatic PICC‐DVT. Risk factors associated with PICC‐DVT included: history of DVT; multi‐lumen PICC; active cancer; presence of another CVC when the PICC was placed; and white blood cell count greater than 12 000. Four risk classes were created based on thrombosis risk. Thrombosis rates were 0.9% for class I, 1.6% for class II, 2.7% for class III and 4.7% for class IV, with marginal predicted probabilities of 0.9% (0.7, 1.2), 1.5% (1.2, 1.9), 2.6% (2.2, 3.0) and 4.5% (3.7, 5.4) for classes I, II, III, and IV, respectively. The risk classification rule was strongly associated with PICC‐DVT, with odds ratios of 1.68 (95% CI, 1.19, 2.37), 2.90 (95% CI, 2.09, 4.01) and 5.20 (95% CI, 3.65, 7.42) for risk classes II, III and IV vs. risk class I, respectively. Conclusion The Michigan PICC‐DVT Risk Score offers a novel way to estimate risk of DVT associated with PICCs and can help inform appropriateness of PICC insertion.