Development of a risk score to predict peripherally inserted central catheter thrombosis in active cancer

Background: Peripherally inserted central catheter (PICC) thrombosis is common. Aims: To explore the prevalence of symptomatic PICC thrombosis and pulmonary embolism (PE)/deep vein thrombosis (DVT) in cancer and non-cancer cohorts. In active cancer, we assessed the Khorana risk score (KRS) and Michigan risk score (MRS) for predicting PICC thrombosis and modifications to improve discriminative accuracy. Methods: We reviewed consecutive cancer patients receiving chemotherapy through a PICC inserted April 2017 to July 2018. For each case, we identified a contemporaneous non-cancer control. Results: Among 147 cancer patients, median age 64 years, PICC duration 70 days (range, 2–452), 7% developed PICC thrombosis (95% confidence interval (CI) 3.6–12.2) and 4% (95% CI 2–9) PE/DVT. Among 147 controls, median age 68 years, PICC duration 18.3 days (range, 0.5–210), 0.7% (95% CI 0–4) developed PICC thrombosis and 2% (95% CI 0.4–6) PE/DVT. In our cancer cohort, no KRS < 1 patients developed PICC thrombosis (95% CI 0–11) compared with 9% (95% CI 5–16) in KRS ≥ 1 (P = 0.12). PICC thrombosis occurred in 4.7% (95% CI 1.5–11.7) MRS ≤ 3 compared with 10.9% (95% CI 4.1–22.2) MRS > 3 (P = 0.32). The addition of thrombocytosis, a variable from KRS, to MRS (modified MRS (mMRS)) improved discriminative value for PICC thrombosis (c-statistic MRS 0.63 (95% CI 0.44–0.82), mMRS 0.72 (95% CI 0.58–0.85)). PICC thrombosis occurred in 1.4% (95% CI 0–8.3) mMRS ≤ 3 and 11.8% (95% CI 6.1–21.2) mMRS > 3 (P = 0.02). More patients were categorised as low risk using mMRS ≤ 3 (47%) than KRS < 1 (22%). Conclusion: Cancer patients had longer PICC durations and higher PICC thrombosis rates than those without (7% vs 0.7%). mMRS more accurately classified low PICC thrombosis risk than KRS <1(47% vs 22%). Prospective validation of mMRS is warranted.