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Diff-Quik is a brand of rapid, three-solution Romanowsky-type stain used on air-dried smears. A methanol-based fixative is followed by an eosin (xanthene) solution and a thiazine (methylene blue and azure) solution, so red-pink and blue-purple cellular components can be told apart in seconds rather than minutes. This guide is general laboratory information, not medical advice or a clinical procedure.
Short answer
“Diff Quik” and “Diff-Quik” name the same family of products: a three-step differential stain. Siemens Healthineers sells it as RAL Diff-Quik and describes it as a simplified alternative to Wright-Giemsa staining that cuts the process from 4 minutes to 15 seconds (a manufacturer claim). Other makers sell comparable kits under their own names, and the dip counts differ between kits, so the kit’s own instructions for use (IFU) govern.
Definition and scope
A Romanowsky stain combines an acidic (anionic) dye and basic (cationic) dyes so that different cell structures take different colours. Diff-Quik-type kits are rapid, dip-based versions. StatLab describes its Hema-Diff kit as “a modified Giemsa/Romanowsky, three step procedure” and lists its uses as fine needle aspirations, cytology, blood smears, bone marrow smears, touch preps and micro-organisms on air-dried smears. For the slower classical methods see Giemsa staining; for different staining families see H&E staining and the Gram stain.
How the three solutions work
Solution 1: fixative
Siemens describes the RAL Diff-Quik fixative as a methanol-based solution that stabilises cellular components on air-dried blood smears.
Solution 2: xanthene (eosin)
Siemens lists solution I as a buffered solution of Eosin Y, an anionic dye, and says it stains cytoplasm pink to yellowish-red.
Solution 3: thiazine
Solution II is a buffered solution of thiazine dyes, which are cationic: methylene blue and Azure A. Siemens attributes the basophilic (blue) staining of nucleoli and cytoplasm to the methylene blue component.
Because the two stains are separate dips, the operator can shift the balance. StatLab’s technical data sheet states that more dips in the xanthene solution intensify the eosinophilic (red) tone, and more dips in the thiazine solution intensify the basophilic (blue) tone. Siemens likewise says its manual protocol lets the user vary staining intensity.
Two manufacturers’ kits side by side
Both kits are described from the manufacturers’ own documents (checked 2026-10-30). The table shows why “Diff-Quik protocol” is not one fixed recipe.
| Feature | Siemens RAL Diff-Quik | StatLab Hema-Diff |
|---|---|---|
| Steps | Three: fixative, solution I, solution II | Three: #1 fixative, #2 xanthene, #3 thiazine |
| Dye chemistry stated | Eosin Y; methylene blue and Azure A | Xanthene and thiazine solutions (dyes not named on the data sheet) |
| Timing stated | Brief immersions in each solution | A short fixative time and a few brief dips in #2 and in #3; exact figures are in the data sheet |
| Finish | Not specified on the product page | Rinse in distilled water, dry; optional xylene dip and coverslip |
| Storage | Not specified on the product page | Room temperature; refer to the safety data sheet |
The practical reading: the immersion counts and times belong to each kit’s IFU, and a laboratory SOP should cite the kit it actually uses.
Expected colours
StatLab’s data sheet gives these results for its kit:
| Cell | Nucleus | Granules | Cytoplasm |
|---|---|---|---|
| Erythrocytes | none listed | none listed | Pink |
| Neutrophils | Purple | Red-lilac | Light pink |
| Eosinophils | Dark blue | Red-orange | Medium blue |
| Basophils | Dark blue | Dark purple | Light blue |
| Monocytes | Violet | none listed | Light blue |
| Lymphocytes | Violet | none listed | Medium blue |
| Platelets | none listed | Purple | Lilac |
Where it matters for labs and supply decisions
- Siemens describes the kit as ready to use, so solutions do not need to be decanted, and lists a stain set of three 0.5 L solutions.
- The kit is three reagents. StatLab lists its three solutions individually and as a set, as a set of #1, #2 and #3.
- Because dip counts and timings differ, a laboratory that changes brand should confirm its staining protocol against the new IFU and update its SOP; this page does not replace either.
- Read the safety data sheet for each solution; StatLab’s data sheet refers users to it.
Slides for the smears themselves are covered in What Is a Microscope Slide?, and cell morphology work in animals in veterinary cytology.
Common misunderstandings
- Diff-Quik is the name of the method. It is a brand; comparable three-step kits exist under other names.
- Every kit uses the same dip count. The two manufacturers describe different timings.
- Rapid means identical to Wright-Giemsa. Siemens calls it a simplified alternative and makes a speed claim; it does not state that results are identical, and neither does this page.
FAQ
Is “diff quik” the same as Diff-Quik stain?
Yes. Both spellings refer to the rapid three-step differential stain sold as RAL Diff-Quik by Siemens Healthineers.
What are the three solutions?
A methanol-based fixative, an eosin (xanthene) solution and a thiazine solution of methylene blue and Azure A, per the Siemens product page.
Which solution gives the red tones and which the blue?
The xanthene (eosin) solution drives the red, eosinophilic tones and the thiazine solution drives the blue, basophilic tones, according to StatLab’s data sheet. Follow the kit’s own instructions for use for any adjustment.
Sources
- Siemens Healthineers, RAL Diff-Quik product page, checked 2026-10-30.
- StatLab Medical Products, Hema-Diff Rapid Differential Stain Technical Data Sheet (revised 2018-08-17), checked 2026-10-30.
