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General product and regulatory information only, drawn from manufacturer documents and the US Code of Federal Regulations. It is not medical advice and not a laboratory procedure. For any real staining run, follow the instructions for use (IFU) that came with your own kit.
Short answer
A Hema 3 stain is a rapid three-solution differential stain for air-dried blood smears: a methanol fixative, a red-to-pink eosin (xanthene) solution and a blue-to-purple thiazine solution. Diff-Quik and Hema-Diff are kits built on the same three-solution design, but their solution names differ, so the IFU for the kit in your lab governs.
Definition and scope
Searches for “hema 3 stain”, “diff quik stain” and “diff quik” point to the same kind of product: a rapid differential stain for blood films and similar air-dried preparations. Three manufacturer documents describe the same layout.
- Thermo Scientific Richard-Allan Scientific Three-Step Stain Set (IFU IS3300, R10/15) is labelled “for in vitro diagnostic use” and “for rapid staining of blood smears”. It names fresh blood films, fresh EDTA blood films and bone marrow films as specimens.
- StatLab Hema-Diff Rapid Differential Stain describes itself as “a modified Giemsa/Romanowsky, three step procedure” and lists fine needle aspirates, cytology, blood smears, bone marrow smears, touch preparations and frozen sections among its uses.
- Siemens Healthineers RAL Diff-Quik is presented as an alternative to Wright-Giemsa staining, with uses listed as blood smears and bone marrow in hematology, piroplasma in veterinary parasitology, spermocytograms and cytology of biological fluids.
For the slower Wright-Giemsa approach that these kits shorten, see Giemsa staining of blood films.
What each solution does
All three documents split the chemistry the same way. The first solution is a methanol-based fixative. The second is an anionic xanthene dye, eosin Y, which colours cytoplasm and eosinophil granules in the pink-to-red range. The third is a cationic thiazine dye mixture (methylene blue and azure A in the Thermo and Siemens kits) that colours nuclei and basophilic structures blue to purple. The Thermo IFU calls the pH of the staining solution and buffer “a critical factor” in the result.
Kit comparison from the manufacturers’ documents
Every cell below comes from the Thermo IFU, the StatLab technical data sheet or the Siemens product page (checked 2026-10-30). “Not stated” means the document does not say.
| Item | Thermo Three-Step Stain Set | StatLab Hema-Diff | Siemens RAL Diff-Quik |
|---|---|---|---|
| Fixative | Methanol fixative | Fixative (#1); composition not stated | Methanol-based fixative |
| Second solution | Solution A: aqueous eosin Y | #2 Xanthene | Solution I: buffered eosin Y (xanthene) |
| Third solution | Solution B: aqueous methylene blue and azure A | #3 Thiazine | Solution II: buffered thiazine dyes (methylene blue and azure A) |
| Named uses | Blood smears, bone marrow films | Blood smears, bone marrow smears, fine needle aspirates, touch preparations, frozen sections | Blood and bone marrow hematology, veterinary piroplasma, spermocytograms, body fluid cytology |
The design is shared, but the naming (A and B, #2 and #3, I and II) is not interchangeable between kits, and each manufacturer’s IFU is the authority for its own product.
The StatLab sheet lists expected colours: neutrophil nuclei purple with red-lilac granules, eosinophil granules red-orange on dark blue nuclei, basophil granules dark purple, lymphocyte nuclei violet and platelet granules purple. The Thermo IFU reports erythrocytes pale pink, eosinophil granules reddish orange and leukocyte nuclei purple.
Storage and handling points in the instructions
- Stock handling: the Thermo IFU says used stain is not returned to the original container.
- Age: stock is not used or diluted after its expiry date, because ripening of the polychromed dye is continuous.
- Quality of dyes: the dyes in that kit are certified by the Biological Stain Commission.
Regulatory class of stain kits
Under 21 CFR 864.1850, dye and chemical solution stains for medical purposes are “mixtures of synthetic or natural dyes or nondye chemicals in solutions used in staining cells and tissues for diagnostic histopathology, cytopathology, or hematology”. They are Class I (general controls) and exempt from 510(k) premarket notification, subject to the limits in 21 CFR 864.9. They are also exempt from the quality management system regulation in part 820 except for records (820.35) and complaint files. Instruments are regulated differently, as the FAQ below shows.
Common misunderstandings
- A stain kit is not an analyzer. It colours cells on a slide for microscopic review; counting is done by a separate device.
- Diff-Quik is the name of the Siemens RAL product. The shared design does not mean every three-solution kit has an identical formulation.
- “Rapid” does not mean the IFU can be skipped: kits differ in naming, composition and instructions.
Frequently asked questions
What is a hematology analyzer?
The FDA regulation for the closest device type, the automated cell counter (21 CFR 864.5200), defines it as a fully or semi-automated device used to count red blood cells, white blood cells or blood platelets in a patient’s peripheral blood sample. It may also measure hemoglobin or hematocrit and red cell indices such as MCV, MCH and MCHC, using electronic particle counting or optical counting. It is Class II. It is a different product from a stain kit: see what an automated cell counter is. For manual counting, see the hemocytometer guide, and for how blood is obtained for films, capillary blood collection.
What is Diff-Quik stain?
Diff-Quik is the Siemens Healthineers RAL brand of rapid three-solution stain: a methanol-based fixative, a buffered eosin Y solution and a buffered thiazine solution of methylene blue and Azure A. Siemens lists blood and bone marrow hematology, veterinary piroplasma, spermocytograms and body fluid cytology as uses.
Sources
All sources checked 2026-10-30.
- Thermo Scientific Richard-Allan Scientific Three-Step Stain Set, Instructions for Use IS3300 R10/15: https://documents.thermofisher.com/TFS-Assets/APD/Instructions/IS3300%20ThreeStepStain%20IFU%20EN.pdf
- StatLab Hema-Diff Rapid Differential Stain, technical data sheet revised 2018-08-17: https://statlab.com/content/pdf/ifu/11970-16.pdf
- Siemens Healthineers, RAL Diff-Quik product page: https://www.siemens-healthineers.com/hematology/ral-diff-quik
- 21 CFR 864.1850, Dye and chemical solution stains: https://www.law.cornell.edu/cfr/text/21/864.1850
- 21 CFR 864.5200, Automated cell counter: https://www.law.cornell.edu/cfr/text/21/864.5200
