Differential Diagnosis

The provided laboratory results show a slight increase in RBC, HGB, and HCT after incubation at 37°C, with minimal changes in other parameters. Based on these findings, the following differential diagnoses can be considered:

• Single most likely diagnosis
  • Cold agglutinin disease: This condition is characterized by the presence of antibodies that agglutinate red blood cells at cold temperatures, leading to an increase in RBC count, hemoglobin, and hematocrit when warmed. The slight increase in these parameters after incubation at 37°C supports this diagnosis.
• Other Likely diagnoses
  • Polycythemia vera: Although the increase in RBC, HGB, and HCT is not dramatic, polycythemia vera could be considered, especially if the patient has other symptoms such as thrombocytosis or leukocytosis.
  • Dehydration: Dehydration can cause a relative increase in RBC, HGB, and HCT due to decreased plasma volume. However, this would not typically be affected by temperature changes.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Paroxysmal cold hemoglobinuria (PCH): This rare condition is characterized by the sudden onset of hemolysis after cold exposure, which could lead to a decrease in RBC, HGB, and HCT. Although the provided results do not show a significant decrease, PCH should be considered due to its potential severity.
  • Sickle cell disease: Although the MCV and MCHC values are within normal limits, sickle cell disease could be considered, especially if the patient has other symptoms such as anemia or jaundice.
• Rare diagnoses
  • Cryohemolysis: This rare condition is characterized by the lysis of red blood cells at cold temperatures, which could lead to a decrease in RBC, HGB, and HCT. However, the provided results do not show a significant decrease, making this diagnosis less likely.
  • Autoimmune hemolytic anemia (AIHA): Although AIHA can cause an increase in RBC, HGB, and HCT due to reticulocytosis, the provided results do not show a significant increase in reticulocyte count, making this diagnosis less likely.