Severe Anemia, Autoagglutination, and a Transfusion Decision
Luna is a 7-year-old, 4.0 kg spayed female Siamese cat presented for lethargy and jaundice. Physical examination shows pale icteric mucous membranes, heart rate 180 beats/min, respiratory rate 32 breaths/min, temperature 39.0°C, and mild splenomegaly. A CBC shows PCV 13%, HCT 14%, total protein 5.8 g/dL, and reticulocyte count 0.4% (absolute 12,800/µL; reference <60,000/µL). The blood smear shows marked autoagglutination and many spherocytes. A saline dispersion test is performed: the agglutination persists after adding saline. The cat's blood type is A. The owner is very anxious and asks whether Luna needs a blood transfusion immediately. The clinic has packed red blood cells and fresh frozen plasma but no blood bank on site. The veterinarian asks you to help interpret the laboratory data and prepare a transfusion plan.
1. Interpret the PCV, total protein, reticulocyte count, and saline dispersion test. What is the most likely diagnosis, and what else would you test to confirm or exclude differentials?
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Interpretation
- PCV 13% / HCT 14% indicates severe anemia. The total protein of 5.8 g/dL is low-normal to mildly low, so the anemia is not simply dilutional from fluids; the cat is also icteric.
- Absolute reticulocyte count 12,800/µL is below the typical 60,000/µL cutoff for regeneration in a cat. This is a nonregenerative anemia, although early immune-mediated hemolytic anemia can be nonregenerative before the marrow responds.
- Saline dispersion test: persistent agglutination after adding saline indicates true autoagglutination rather than rouleaux. That is a strong clue for immune-mediated hemolytic anemia, especially with spherocytes and jaundice.
Most likely diagnosis
Immune-mediated hemolytic anemia, possibly secondary to infection, neoplasia, or drug exposure. In a cat, differentials include Mycoplasma haemofelis infection, FeLV/FIV, feline infectious peritonitis, and Heinz body anemia from toxins or oxidative drugs.
Additional testing
Test FeLV/FIV, perform a Mycoplasma PCR or careful blood smear review, check blood glucose and liver enzymes, and evaluate for DIC if bleeding or thrombocytopenia is present. A Coombs test can support IMHA but is not required when autoagglutination is present. Blood culture or imaging may be indicated if fever or splenomegaly suggests infection or neoplasia.
2. Luna's PCV is 13%. Describe how you would decide whether to transfuse, including blood typing, crossmatching, and monitoring.
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Transfusion is not based on a single PCV value. Consider clinical signs of inadequate oxygen delivery: tachycardia, tachypnea, weakness, collapse, altered mentation, and poor perfusion. A PCV of 13% is low, but a stable cat may be managed briefly while diagnostics are completed; a cat with respiratory distress, seizures, or cardiovascular instability needs transfusion support sooner.
Typing and crossmatching
Luna is type A. Cats have naturally occurring alloantibodies, so type A blood is preferred for a type A cat, but a major and minor crossmatch should still be performed because previous transfusion or pregnancy can sensitize the cat. Do not assume that 'type A to type A' eliminates all reaction risk.
Transfusion plan
Packed red blood cells are appropriate if volume overload is a concern. A typical starting dose is 10–15 mL/kg, so for 4.0 kg: 40–60 mL. Give slowly over 2–4 hours through a filter, using a dedicated line. Baseline vitals, PCV, and temperature should be recorded. Monitor every 15 minutes initially for fever, tachycardia, hypotension, hemoglobinuria, vomiting, or respiratory difficulty. Stop the transfusion and notify the veterinarian if a reaction occurs. Recheck PCV after transfusion, but do not expect an immediate rise to normal.
3. What sample handling errors could make agglutination worse, and how would you report the findings to the veterinarian?
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Sample handling errors
- Refrigeration can promote cold agglutination and make rouleaux or agglutination appear worse. Blood should be evaluated promptly at room temperature when possible.
- Rough handling, vigorous shaking, or forcing blood through a small needle can cause hemolysis, which confuses interpretation.
- Delayed processing can allow cells to settle and alter smear quality.
- Using the wrong anticoagulant or an underfilled EDTA tube can create artifacts.
- Reading the saline dispersion test too quickly or without a control can lead to a false interpretation.
Reporting
The report should be specific and actionable: 'Marked autoagglutination observed on the direct smear; agglutination persisted after saline dispersion, consistent with true autoagglutination rather than rouleaux. Many spherocytes seen. PCV 13%, total protein 5.8 g/dL, absolute reticulocyte count 12,800/µL (nonregenerative).' Include the cat's blood type and crossmatch status. Avoid writing only 'agglutination present,' because the veterinarian needs to know whether it persisted after saline and whether spherocytes were seen. Recommend correlation with FeLV/FIV and Mycoplasma testing, and flag the sample for immediate review if the cat is unstable.