THE DISCRIMINATING VALUE OF SERUM LACTATE-DEHYDROGENASE LEVELS IN CHILDREN WITH MALIGNANT NEOPLASMS PRESENTING AS JOINT PAIN

Objectives: To determine if serum lactate dehydrogenase levels disting uish patients with malignant neoplasm presenting with musculoskeletal complaints from patients with juvenile rheumatoid arthritis who report ed similar symptoms. Design: Retrospective case-comparison study. Sett ing: Tertiary care, outpatient clinics. Patients: Twelve patients with malignant neoplasms who presented with arthritis or arthralgias and n ormal complete blood cell counts and blood smears in whom rheumatologi c diagnosis was initially made were compared with 24 children with a f inal diagnosis of juvenile rheumatoid arthritis. The patients with mal ignant neoplasms all had normal blood counts and elevated sedimentatio n rates at symptom onset. Interventions: None. Results: Serum lactate dehydrogenase levels were significantly higher in the cancer patients at 2.2 times the high normal values vs 0.8 times high normal for patie nts with juvenile rheumatoid arthritis (P=.004, Mann-Whitney U test). No significant differences were observed in white blood cell counts, h emoglobin levels, platelet counts, erythrocyte sedimentation rate, or uric acid or aspartate aminotransferase levels at initial evaluation. Conclusion: Serum lactate dehydrogenase values may distinguish patient s with malignant neoplasms from those with rheumatic disease early in the course of illness when symptoms and other laboratory values are no t helpful.