Can we lower the platelet threshold of ≥ 50 × 10/L for performing a lumbar puncture safely in patients with hematological malignancies?

Lumbar punctures (LP) are routinely used to administer intrathecal chemotherapy for children and adults with hematologic malignancies. The current guidelines suggest a platelet threshold of ≥ 50 × 10/L prior to LP for intrathecal chemotherapy (ITC). This can be challenging in patients with hematological malignancies who are thrombocytopenic. We conducted a retrospective chart review of 900 LPs for ITC and compared adverse events in patients with a platelet count of ≥ 50 × 10/L and < 50 × 10/L. Cohort 1 included 682 LPs (75.8%) with a pre-procedure platelet count ≥ 50 × 10/L, and cohort 2 included 218 LPs (24.2%) with a pre-procedure platelet count < 50 × 10/L. Cohort 2 was further subdivided into pre-procedure platelet counts of 41 × 10/L-49 × 10/L (n = 43), 31 × 10/L-40 × 10/L (n = 77), 21 × 10/L-30 × 10/L (n = 84), and 11 × 10/L-20 × 10/L (n = 14). Among 900 LP procedures, a pre-procedure platelet count < 50 × 10/L did not demonstrate a higher rate of post-procedure adverse events (6.5% vs 6.8%, p = 0.8237). When cohort 2 was further stratified, the cohort with a pre-procedure platelet count of 21 × 10/L-30 × 10/L had the highest percentage of complications from LP (9.5%) and the highest rates of traumatic taps with observed LP RBC count > 200 (35.7%, p = 0.0015). The rate of red blood cells (RBC) in the CSF was significantly higher in the group with platelets < 50 × 10/L with observed LP RBC count ≥ 200 (31.2% vs 20.5%, p = 0.0016), ≥ 500 (27.1% vs 14.6%, p < 0.0001), and ≥ 1000 (23% vs 11.6%, p < 0.0001). No instances of epidural hematomas were seen. We found no significant difference in bleeding complications between patients undergoing LPs for ITC with a platelet count above or below 50 × 10/L.