35225 Undifferentiated Pruritus and the Risk of Hematologic Malignancy

Background: Pruritus is common among patients with hematologic malignancies (HMs). However, the risk of HM among patients with pruritus is not established. Additionally, the diagnostic utility of serum lactate dehydrogenase (LDH), frequently ordered to assess malignancy in pruritic patients, remains uncertain. Methods: A population-level analysis from 2002-2020 was conducted with TriNetX, a global health research network. Patients were identified using ICD-9 and ICD-10 codes for undifferentiated pruritus, excluding patients with chronic pruritic dermatoses or systemic disease-associated pruritus. Patients were age-, sex-, race-, BMI-, and smoking/alcohol status-matched to controls without diagnosis of pruritus. SNOMED-CT and General Equivalence Mappings were used to map diagnostic codes prior to the introduction of ICD-10. P values were adjusted for multiple hypothesis testing using the Benjamini-Hochberg method. Results: 327,502 patients with undifferentiated pruritus and 8,934,671 controls were identified. Within 12 months of diagnosis with pruritus, patients had increased risk of Hodgkin’s lymphoma (relative risk [RR] 4.42, 95% confidence interval [CI] 2.83-6.88), non-Hodgkin’s lymphoma (RR 2.35, 95% CI 1.96-2.82), multiple myeloma (RR 2.38, 95% CI 1.66-3.41), lymphocytic leukemia (RR 1.47, 95% CI 1.07-2.02), myeloid leukemia (RR 2.56, 95% CI 1.79-3.67), monoclonal gammopathy (RR 1.90, 95% CI of 1.55-2.32), and myelodysplastic syndrome (RR 1.74, 95% CI 1.14-2.64). Pruritic patients had higher serum LDH (297.55 ± 310.9 units/liter) compared with controls (255.51 ± 223.73 units/liter), but LDH >250 units/liter did not confer a higher risk of developing HM in either group. Conclusion: Patients with undifferentiated pruritus have increased risk of developing HM, and LDH has limited diagnostic utility in these patients.