Norm of Ferric Chloride Test
No color change when the diagnostic reagent (ferric chloride) is added to the urine.
Usage of Ferric Chloride Test
Of value in the diagnosis of epidemic dropsy and certain drug intoxications (salicylates and phenothiazines), and in the diagnosis of several inborn errors of amino acid metabolism (phenylketonuria, maple syrup urine disease, and alkaptonuria). Also occasionally used to detect melanin in the urine.
Description of Ferric Chloride Test
A spot urine sample is obtained. Ferric chloride solution is added to the urine sample, and characteristic color changes occur depending on the pathologic condition present (that is, purple with salicylates, purple-pink with phenothiazines, gray with melanin, for example).
Color Change in Urine
|Alcoholism||Red or red-brown|
|Alkaptonuria||Blue or green, fades quickly|
|Diabetes||Red or red-brown|
|Histidinemia||Green or blue-green|
|Maple syrup urine disease||Blue|
|Phenylketonuria||Blue or blue-green, fades to yellow|
|Starvation||Red or red-brown|
|Tyrosinosis||Green, fades in seconds|
|Alpha-ketobutyricacid||Purple, fades to red-brown|
|Pyruvic acid||Deep gold-yellow or green|
|Xanthurenic acid||Deep green, later brown|
Professional Considerations of Ferric Chloride Test
Consent form NOT required.
- Several drugs can influence the test and cause a color change when the ferric chloride reagent is added to the urine. These include salicylates (aspirin and related drugs) and phenothiazine-related compounds. These should be avoided if possible before the test.
- Fasting is not required before the test, and no other pretest preparation is necessary.
- Urine is collected from the client into a clean container and submitted to the diagnostic laboratory for analysis.
- In the laboratory ferric chloride is added to the urine sample, and the technician waits for a color change to occur.
- No special postprocedure care of the client is required.
Client and Family Teaching
- The client and appropriate family members should be oriented as to the rationale behind the test before it is performed.
- Several of the conditions diagnosed with this test represent inborn errors of metabolism.
- Genetic counseling may be indicated once the diagnosis of these disorders is established.
Factors That Affect Results
- Preparation and storage of the ferric chloride reagent.
- Ingestion of certain drugs (salicylates and phenothiazines) may cause a color change when the ferric chloride is added to the urine sample.
- The ferric chloride test is rather insensitive because it relies on a gross (qualitative) color change observed by a technician. Other more sensitive tests (including chromatography) may be helpful in the diagnosis of several of the disorders listed above