Introduction: Patients with hematologic malignancies frequently require lumbar punctures (LPs) for administration of intrathecal chemotherapy. With myelosuppressive chemotherapy, thrombocytopenia is common and patients often require platelet transfusions in order to reduce the risk of bleeding during invasive procedures. However, there is a dearth of evidence supporting a platelet threshold required for LPs. Guidelines from the American Association of Blood Banks recommend a minimum platelet count of 50 x 103/µL, but this is based largely on expert opinion. Platelet transfusion is associated with risk of transfusion reaction and alloimmunization, cost, and procedural delays. Given these risks, we instituted a reduction in platelet threshold to 40 x 103/µL for lumbar puncture. We retrospectively reviewed patient outcomes to assess the safety and efficacy of this approach.

Methods: In November 2017, a platelet count threshold for LPs was introduced for adult oncology patients in both the inpatient and outpatient settings at Froedtert and the Medical College of Wisconsin. Previous guidelines recommended a platelet count of 50 x 103/µL in order to undergo a lumbar puncture. This threshold was decreased to 40 x 103/µL for oncology patients. Guidelines were agreed upon and implemented in all procedure settings: the inpatient procedure team, the outpatient procedure suite, and the radiology department (for fluoroscopy-guided lumbar puncture). Data regarding the pre-procedure platelet count, number of platelet transfusions given per procedure, CSF RBCs, and occurrence of post-procedure spinal hematomas were collected through the electronic medical record.

Results: From November 1, 2016 to May 1, 2018 267 oncology patients underwent a lumbar puncture. Oncologic diagnosis was NHL, ALL, AML, solid malignancy, or other hematologic malignancy/disorder in 26%, 23%, 18%, 16%, and 17%, respectively. 42% of were female. A total of 845 LPs were performed under fluoroscopy, with ultrasound guidance, and by an experienced provider in 26%, 58%, and 16% of cases respectively. 534 LPs (63%) were performed with a platelet transfusion threshold of 50 x 103/µL (Plt≥50) and 311 LPs (37%) were performed with a platelet transfusion threshold of 40 x 103/µL (Plt≥40). The average pre-LP platelet count was 152.8 x 103/µL in the Plt≥50 group and 138.4 x 103/µL in the Plt≥40 group. 79 patients in the Plt≥50 group and 42 patients in the Plt≥40 group had a recorded platelet count between 40-49 x 103/µL within 24 hours prior to the procedure. After institution of the new guidelines, 40 LPs were performed with a platelet count < 50 x 103/µL. The average number of units of platelets transfused per procedure significantly decreased from 0.58 to 0.39 after lowering the transfusion threshold (p < 0.05). One lumbar epidural hematoma occurred post-intervention and one lumbar subarachnoid hematoma occurred pre-intervention, both in patients whose pre-procedure platelet counts were > 100 x 103/µL. No traumatic hematomas were observed in patients whose pre-procedure platelet count was < 50 x 103/µL. The incidence of traumatic taps (identified as CSF red blood cells > 10/µL) was significantly higher in patients whose pre-procedure platelet count was < 50 x 103/µL (64% vs. 46%, p <0.05).

Conclusion: Decreasing the LP platelet transfusion threshold from 50 x 103/µL to 40 x 103/µL significantly reduced platelet transfusions. This was not associated with an increased risk of complications. However, the incidence of traumatic taps was significantly higher in patients with a platelet count < 50 x 103/µL. Given that the average cost of one unit of platelets is approximately $500 and 40 procedures were performed with a platelet count < 50 x 103/µL, decreasing the platelet transfusion threshold resulted in a cost savings of approximately$20,000 over the course of 6 months, not including administrative costs. Overall, this data suggests that lowering the platelet transfusion threshold for lumbar punctures to 40 x 103/µL is both safe and cost effective for oncology patients.

Disclosures

Atallah:Abbvie: Consultancy; Jazz: Consultancy; Novartis: Consultancy; BMS: Consultancy; Pfizer: Consultancy.

## Author notes

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Asterisk with author names denotes non-ASH members.