What other lab findings might be present in a patient on sulfasalazine (azulfidine) with anemia (low hemoglobin)?

Laboratory Findings Associated with Sulfasalazine-Induced Anemia

Patients on sulfasalazine with a hemoglobin of 9.1 g/dL should be evaluated for multiple potential hematologic abnormalities including decreased reticulocyte count, folate deficiency, hemolysis, and bone marrow suppression. 1

Common Laboratory Abnormalities

• Complete blood count abnormalities:

  • Decreased reticulocyte count indicating impaired bone marrow response 2
  • Macrocytosis (elevated MCV) suggesting folate deficiency 3, 4
  • Contracted red blood cells related to dose and serum sulfapyridine levels 4

• Iron studies:

  • Normal or elevated ferritin (unlike typical iron deficiency anemia) 2
  • Decreased transferrin saturation suggesting functional iron deficiency 2

• Evidence of hemolysis:

  • Elevated reticulocyte count (>5%) in 53% of patients with sulfasalazine-induced hemolysis 5
  • Heinz bodies in peripheral blood smear (present in 47% of patients with hemolysis) 5
  • Elevated indirect bilirubin and LDH 6

• Folate-related findings:

  • Decreased serum folate levels 3
  • Impaired folate absorption (sulfasalazine reduces folate absorption by 7-16%) 3
  • Megaloblastic changes in bone marrow if folate deficiency is severe 7

Monitoring Recommendations

• CBC, liver function tests, and renal function should be monitored within the first 1-2 months of sulfasalazine usage and every 3-4 months thereafter 2

• Dose reduction or temporary discontinuation is conditionally recommended if:

  • Clinically relevant elevation in liver function tests occurs 2
  • Decreased neutrophil or platelet count is found 2

Mechanism of Sulfasalazine-Induced Anemia

Sulfasalazine can cause anemia through multiple mechanisms:

• Hemolysis: Occurs in up to 43% of patients on sulfasalazine, correlating with serum sulfapyridine levels rather than sulfasalazine levels 5

• Folate deficiency: Sulfasalazine impairs folate absorption, which becomes clinically significant when other risk factors for folate deficiency are present 3

• Bone marrow suppression: Direct toxic effect on erythropoiesis 1

• G6PD deficiency: Patients with this condition are at higher risk for hemolytic anemia when taking sulfasalazine 1

Important Considerations

• Anemia is not a characteristic of inflammatory bowel disease itself; finding anemia should prompt thorough investigation of drug-related causes 2

• Lower doses of sulfasalazine (1.5 g/day) are associated with fewer red cell abnormalities than higher doses (2.5 g/day) 4

• Patients with glucose-6-phosphate dehydrogenase deficiency should be monitored closely for signs of hemolytic anemia 1

• Complete blood counts, including differential white cell count and liver function tests, should be performed every two weeks during the first three months of therapy 1

• The presence of sore throat, fever, pallor, purpura, or jaundice may indicate a serious blood disorder requiring immediate medical attention 1