What is the least appropriate step in investigating a transfusion reaction characterized by fever, chills, and hypertension in a patient who received a platelet transfusion?

Ordering BNP Test is the LEAST Appropriate Step in Investigating this Transfusion Reaction

The least appropriate step in investigating this transfusion reaction is ordering a BNP (brain natriuretic peptide) test, as this patient is experiencing a febrile non-hemolytic transfusion reaction (FNHTR) rather than transfusion-associated circulatory overload (TACO). 1

Clinical Presentation Analysis

The patient's presentation shows classic signs of a febrile non-hemolytic transfusion reaction:

• Spike in temperature (from 36.8°C to 39.1°C)
• Chills
• Timing: near the end of platelet transfusion
• Prompt resolution with antipyretic treatment
• No signs of respiratory distress or pulmonary edema

The mild hypertension (from 126/82 to 158/88 mmHg) is likely part of the physiologic response to fever rather than indicating volume overload.

Appropriate Diagnostic Steps

1. Gram Stain and Culture of Platelet Product

• Essential to rule out bacterial contamination, which can cause similar symptoms
• Platelet products have higher risk of bacterial contamination compared to other blood components 1
• Febrile reactions are the most common immediate incident related to platelet transfusions 2

2. Post-transfusion DAT (Direct Antiglobulin Test)

• Important to rule out immune-mediated hemolytic reaction
• Can help distinguish between immune and non-immune causes of the reaction
• Should be performed even though hemolysis is less likely with platelet transfusions

3. Bilirubin Test

• Helps detect hemolysis which may not be clinically apparent
• Elevated bilirubin could indicate a hemolytic reaction requiring further investigation

Why BNP Testing is Inappropriate

BNP testing would be indicated if:

• Patient showed signs of TACO (transfusion-associated circulatory overload) such as:
  • Respiratory distress or dyspnea
  • Pulmonary edema
  • Significant hypertension with evidence of fluid overload
  • Jugular venous distension
  • S3 gallop on cardiac examination 1, 3

In this case:

• The patient has no respiratory symptoms
• The reaction resolved with antipyretic alone (not diuretics)
• The clinical picture is consistent with FNHTR rather than TACO

Pathophysiology of Febrile Non-Hemolytic Transfusion Reaction

FNHTRs with platelets are primarily caused by:

1. Accumulation of cytokines in the platelet product during storage 4, 5
2. Possible interaction between recipient antibodies and donor leukocytes
3. Release of biologic response modifiers during platelet storage 4

The risk of FNHTR increases with:

• Longer storage time of platelet concentrates 2
• Higher leukocyte content in the transfused product
• Previous alloimmunization in multi-transfused patients

Common Pitfalls to Avoid

1. Misdiagnosing FNHTR as TACO: This could lead to unnecessary diuretic treatment and delay appropriate management.

2. Failing to culture the platelet product: Bacterial contamination can present similarly to FNHTR but requires immediate antibiotic treatment.

3. Sampling errors: When collecting samples for bacterial culture, avoid drawing from the distal end of transfusion sets as this can lead to false-positive results due to reflux of patient's blood 6.

4. Not considering interdonor incompatibility: In multi-transfused patients, reactions can occur due to incompatibility between products from different donors 7.

By correctly identifying this reaction as an FNHTR rather than TACO, the appropriate investigation can be pursued without unnecessary testing, and preventive measures can be implemented for future transfusions, such as leukoreduction or premedication with antipyretics.