Urinalysis and Body Fluids 6th Edition by Majorie DiLorenzo, Susan Strasinger

Exercise 73

The primary problem with urobilinogen tests using Ehrlich reagent is:

A. Positive reactions with porphobilinogen

B. Lack of specificity

C. Positive reactions with Ehrlich’s reactive substances

D. All of the above

Step 1 of 2

Porphobilinogen Interference in urobilinogen reagent strip test:

The reaction uses Ehrlich’s aldehyde reaction that is called Ehrlich-reactive compounds which produce false positive and false negative results.

False positive reactions:

• If a substance actually not present in a test and the test result will give presence of the substance mistakenly.

The compounds interfere are:

• Indican

• Porphobilinogen

• p-aminosalicylicacid

• methyldopa

• sulphonamides

• procaine

• chlorpromazine

Porphobilinogen:

It is involved in metabolism of porphyrin (pigment) and it is a pyrrole.

• Porphobilinogen interferes in urobilinogen test and give false positive result for porphobilinogen in urine when using Ehrlich reagent.

• It is the primary difficult in detecting urobilinogen using Ehrlich reagent.

• Porphobilinogen presence in urine is significant clinically but detection of porphobilinogen in reagent strip is not a consistent method.

Therefore, “positive reaction with porphobilinogen” is the primary difficult of using Ehrlich reagent in urobilinogen test. Hence, the correct answer is option.