Investigations
1st investigations to order
clinical history and examination
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
Investigations to consider
cultures (e.g., blood or wound)
Test
Indicated only for the specific presentation of suspected infection.
Cultures may be positive when patients inject saliva or faeces in order to cause infections in the blood or wounds.[24]
Result
possible polymicrobial cultures or atypical organisms
serum C-peptide
Test
Indicated only for the specific presentation of hypoglycaemia.
C-peptide will be low in instances of self-induced hypoglycaemia by injection of exogenous insulin.[24]
Historically, insulin antibodies were useful when hypoglycaemia 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 hypoglycaemia by injection of exogenous insulin: low level
urine sulphonylureas
Test
Indicated only in the specific presentation of hypoglycaemia. Sulphonylurea (e.g., glyburide) may be present in the urine if the patient ingests oral hypoglycaemic agents in order to induce hypoglycaemia.[24] A good assay is required.
Factitious meglitinide (repaglinide)-induced hypoglycaemia has been reported, in addition to hypoglycaemia induced by sulphonylureas.
Result
ingestion of oral hypoglycaemic agents: positive
urine electrolytes
Test
Indicated only in the specific presentation of electrolyte abnormality.
Urine potassium may be elevated if the patient ingests diuretics in order 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 in order to feign proteinuria.[24]
Result
addition of exogenous protein to urine: variable levels
serum thyroglobulin
Test
Indicated only in the specific presentation of hyperthyroidism.
Serum thyroglobulin will be low when a patient is ingesting thyroid hormone in order to simulate hyperthyroidism.[24]
Result
ingestion of thyroid hormone: low
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