Tests
1st tests to order
clinical history and exam
Test
No tests are broadly indicated for factitious disorder. Certain specific tests may be required depending on the specific presentation.
Irregular finding on diagnostic tests may be the most solid evidence that illness is fabricated. In general, when factitious illness is strongly suspected, invasive and expensive diagnostic tests should be avoided unless absolutely necessary either to establish diagnosis or for patient safety.
Result
diagnosis is clinical; tests may not be indicated
Tests to consider
cultures (e.g., blood or wound)
Test
Only indicated for the specific presentation of suspected infection.
Cultures may be positive when patients inject saliva or feces to cause infections in the blood or wounds.[24]
Result
possible polymicrobial cultures or atypical organisms
serum C-peptide
Test
Only indicated for the specific presentation of hypoglycemia.
C-peptide will be low in instances of self-induced hypoglycemia by injection of exogenous insulin.[24]
Historically, insulin antibodies were useful when hypoglycemia was induced by pork or beef insulin. These have become less useful now that human insulin is mainly used. There are also cases of spontaneously occurring antibodies, which complicate interpretation of results.
Result
self-induced hypoglycemia by injection of exogenous insulin: low level
urine sulfonylureas
Test
Only indicated in the specific presentation of hypoglycemia. Sulfonylurea (e.g., glyburide) may be present in the urine if the patient ingests oral hypoglycemic agents to induce hypoglycemia.[24] A good assay is required.
Factitious meglitinide (repaglinide)-induced hypoglycemia has been reported, in addition to hypoglycemia induced by sulfonylureas.
Result
ingestion of oral hypoglycemic agents: positive
urine electrolytes
Test
Only indicated in the specific presentation of electrolyte abnormality.
Urine potassium may be elevated if the patient ingests diuretics to induce electrolyte abnormalities.[24]
Result
ingestion of diuretics: elevated urine potassium
urine protein
Test
Protein may be widely variable in the urine if the patient adds exogenous protein such as egg white to the urine to feign proteinuria.[24]
Result
addition of exogenous protein to urine: variable levels
serum thyroglobulin
Test
Only indicated in the specific presentation of hyperthyroidism.
Serum thyroglobulin will be low when a patient is ingesting thyroid hormone to simulate hyperthyroidism.[24]
Result
ingestion of thyroid hormone: low
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