Patients who may be at risk for a serious allergic reaction to protamine sulfate:
(1) previous history of an allergic reaction to protamine sulfate
(2) fish allergy (to "true vertebrate" fish and not shellfish)
(3) man after vasectomy (a large percentage of patients develop antiprotamine antibodies)
(4) diabetic treated in the past with NPH insulin ("P" indicates protamine)
(5) previous administration of protamine sulfate (as heparin reversal)
A history of a previous reaction indicates a high risk of recurrence. The other risk factors may be associated with a reaction but these are uncommon.
Testing that can be performed:
(1) skin testing using protamine sulfate solution: sensitive but not specific; simple but a patient may have an anaphylactic reaction
(2) RAST (radioallergosorbent test): less sensitive but more specific than skin testing; avoids risk of an anaphylactic reaction; technically complex
(3) ELISA testing: less sensitive but more specific than skin testing; avoids risk of an anaphylactic reaction; technically complex
(4) leukocyte histamine release test: less sensitivity but greater specificity than skin testing; avoids risk of an anaphylactic reaction; technically complex
Protocol for skin testing:
(1) Do not test within 4 weeks of a previous reaction.
(2) Be prepared to treat a possible anaphylactic reaction.
(3) Prepare a sterile solution of protamine sulfate with 1 mg/L.
(4) Inject 0.01 to 0.02 mL of the solution subcutaneously.
(5) A reaction is positive if (a) there is a wheal is > 10 mm (b) for > 30 minutes after the injection.
