Cat. no. Z83 Sudan Black IV Stain 15ml


Hardy Diagnostics Sudan Black IV Stain is recommended for use in microscopic detection of fecal fat due to malabsorbtion.


Sudan Black IV Stain, also known as scarlet red, was introduced by Michaelis in 1901 as a fat stain.(6) It is a dimethyl derivative of Sudan III, which makes it a deeper and more intense stain, yet it has similar physical properties and is fat soluble.(6) This stain has been widely used as a screening method, because it is easy to use and correlates well with quantitative methods.(4)

Sudan Black IV Stain is used as a qualitative method to detect the presence of fecal fat. Normally the stool will not contain more than 20 grams of fat daily.(7) In the case of steatorrhea, fat malabsorbtion occurs, and greater quantities of fat are detected in the stool. This procedure, when performed carefully and consistently, is a simple method of detecting this condition in the patient.


Approximate ingredients per liter:

Sudan Black IV, Certified 3.0mg
Ethanol, 95% 740.0ml
Deionized Water 260.0ml


Upon receipt store at 2-30ºC. Products should not be used if there are any signs of contamination, deterioration, or if the expiration date has passed. Do not expose to excessive heat or moisture.



Specimen Collection: Consult listed references for information on specimen collection.(1,5)

For optimum results, fresh, unpreserved fecal material is required. If there is to be a time delay prior to testing, the specimen should be refrigerated immediately after collection. Specimens greater than 48 hours old or specimens that are dried out should be recollected under optimum conditions.(2,3)

Place a small aliquot of stool suspension on a clean glass slide. Mix two drops of 95% ethanol with the suspension on the slide. Add two drops of Sudan Black IV Stain to the suspension on the slide and mix well. Cover the suspension with a coverslip and examine microscopically for the presence of large orange or red droplets.


It is recommended that positive controls be run in parallel with patient specimens and that results from this staining procedure be reported only if positive control smears are acceptable.

Neutral fats appear as large orange or red droplets. If 60 or more stained droplets (neutral fats) are seen per 400X (high power) field, then it is a presumptive finding that the patient has steatorrhea.(4)

Fatty acids are present as lightly staining flakes or "needle-like" crystals that do not stain. Soaps will appear as non-staining formless flakes, coarse crystals, or rounded masses.(3)


Caution must be taken when interpreting the slide, as castor oil and mineral oil may mimic the appearance of neutral fats. Neutral fat globules are generally absent or very rare in normal stool specimens. Therefore, the presence of large quantities of neutral fat may indicate that the patient has ingested mineral oil or castor oil, thus causing a false-positive result.(3)

Fatty acids may not be visible when they stain as "needle-like" crystals.(4)

Do not count fat present in vegetable cells when reporting results.(3)

To obtain accurate, repeatable results using the Sudan Black IV staining method, it is very important that only skilled technologists able to maintain very consistent results perform this test.(7)


Standard microbiological supplies and equipment such as slides, coverslips, microscopes, pipets, applicator sticks, collection bottles, and 95% ethanol, etc., as well as serological and biochemical reagents, are not provided.

Quality Control

User Quality Control

Mineral oil or mayonnaise may be used as a positive staining control.(3)

Water may be used as a negative staining control.

The microscope should be calibrated (within the last 12 months), and the objectives and oculars used for the calibration procedure should be in place on the microscope when objects are measured.(1,5)


Sudan Black IV Stain should appear dark reddish-orange in color.


1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Drummey, B.S., J.A. Benson, Jr, and C.M. Jones. 1961. Microscopic examination of the stool for steatorrhea. N. Engl. J. Med.; 264:85-7.

3. Garcia, L. S. 2007. Diagnostic Medical Parasitology, 5th ed. ASM Press, Washington, D.C.

4. Henry, J.B., ed. 1979. Clinical Diagnosis and Management, 16th ed. Vol. I. W.B. Saunders Company, Philadelphia, PA.

5. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

6. Lillie, R.D. 1977. H. J. Conn's Biological Stains, 9th ed. Williams & Wilkins Company, Baltimore, MD. Reprint by Sigma Chemical Company, 1991.

7. Tilton, R.C., A. Balows, et al. 1992. Clinical Laboratory Medicine, Mosby Year Book, St. Louis, Missouri.