ASCP HT Exam Prep
For HT(ASCP) testing dates from November 1, 2026 onward, ASCP uses a revised content guideline. Everything below is built on it. Start with the priority map, then work the 25 practice questions. The answer and explanation sit under each one.
Where the points are
The exam is 100 questions in 2 hours 30 minutes. ASCP sets a percentage range for each of five content areas (ASCP HT/HTL content guideline, p. 1):
| Content area | Share of exam | What to drill first |
|---|---|---|
| Staining | 30–40% | What each stain shows, its color result, and why it fails |
| Fixation | 15–25% | Fixative types, volume ratio, timing, pigments, the new named fixative list |
| Embedding/Microtomy | 15–25% | Orientation, section thickness by stain, frozen sections, instrument troubleshooting |
| Processing | 10–20% | Dehydration → clearing → infiltration, decalcification |
| Laboratory Operations | 10–15% | Chemical and fire safety, exposure limits, infection control, lab math, regulations |
New for HT since November 1, 2026: laboratory regulations (CLIA, CAP, HIPAA, proficiency testing and more) are no longer HTL-only. Safety is spelled out in detail, and there's a named list of fixatives. IHC narrowed to terminology plus fixation and processing. If your study materials use an older outline, see what changed.
Start here today:
- Work the 25 questions below without notes.
- Mark every miss in an error log by content area.
- Pick the 4-week plan or one of its 2-, 6- or 8-week versions.
- Keep the current ASCP guideline open as your checklist.
25 practice questions for the HT exam
These are original, unofficial practice questions written by Castleport Test Prep for study. They are not ASCP questions. They're spread across all five areas in roughly the guideline's proportions. Your score on them is feedback on these 25 items, not an ASCP scaled score or a prediction of passing.
Fixation
HT-PREP-001.
A specimen measures 4 cm × 3 cm × 0.4 cm. Which container volume of 10% neutral buffered formalin (NBF) is the smallest that still meets a 20:1 fixative-to-tissue ratio?
Show answer
Answer: D. 100 mL
Tissue volume = 4 × 3 × 0.4 = 4.8 cm³, which is about 4.8 mL. Twenty times that is 96 mL, so 100 mL is the smallest choice that works. A, B and C all fall short and risk under-fixed centers. Formaldehyde penetrates quickly, but its cross-linking reactions are slow, which is why both volume and thin slicing (3–4 mm) matter. Source: Dako/Agilent Special Stains and H&E, Ch. 16, p. 143.
HT-PREP-002.
"10% neutral buffered formalin" contains approximately what concentration of formaldehyde?
Show answer
Answer: B. 4%
Commercial formalin is about 40% formaldehyde. "10% formalin" is a tenfold dilution of that stock, which gives about 4% formaldehyde. C is the classic trap: the 10% describes the formalin, not the formaldehyde. D is the undiluted stock. Source: Dako/Agilent, Ch. 16, p. 142.
HT-PREP-003.
A skin biopsy needs direct immunofluorescence at a reference laboratory, and it can't be snap-frozen before shipping. Which transport medium on ASCP's fixative list fits this job?
Show answer
Answer: B. Michel medium
Biopsies for direct immunofluorescence are usually snap-frozen in liquid nitrogen. When that isn't practical, they are commonly placed in Michel medium for transport. NBF (A), Bouin (C) and Carnoy (D) are fixatives for routine paraffin histology, not the transport options described for immunofluorescence specimens. Source: ARUP Laboratories, Direct Immunofluorescence Tissue Biopsy specimen requirements. Michel medium is also named on the ASCP fixative/transport media list, p. 5.
HT-PREP-004.
A synovial biopsy comes with a history of gout, and the pathologist wants urate crystals preserved. The best fixative is:
Show answer
Answer: B. Absolute or 95% ethanol
Sodium urate crystals dissolve in water, so an aqueous fixative such as NBF (A) can wash them out before anyone sees them. Alcohol fixes the tissue without dissolving them. Bouin (C) and Zenker (D) are aqueous too. Source: Dako/Agilent, Ch. 16, pp. 145–147.
HT-PREP-005.
An immunohistochemical stain is unexpectedly weak on a specimen that remained in 10% NBF much longer than the laboratory's validated fixation time. Which preanalytic factor should be investigated first?
Show answer
Answer: A. Fixation duration
Formaldehyde fixation can alter antigen accessibility, so fixation time is a direct preanalytic variable when IHC staining is weaker than expected. The current HT outline includes IHC terminology plus fixation and processing effects; antigen-retrieval techniques themselves are marked HTL-only. B, C and D do not explain this preanalytic IHC problem. Sources: ASCP HT/HTL content guideline, pp. 2 and 6; Dako, Ch. 16, p. 141.
Processing
HT-PREP-006.
After fixation, which sequence correctly prepares tissue for paraffin embedding?
Show answer
Answer: D. Dehydration → clearing → infiltration
Water and paraffin don't mix. Alcohols first replace the water. Then a clearing agent such as xylene, which mixes with both alcohol and paraffin, replaces the alcohol. Finally, melted paraffin replaces the clearing agent. Every other order puts two liquids that won't mix back to back. Source: Dako/Agilent, Ch. 16, p. 148.
HT-PREP-007.
Why is a clearing agent such as xylene used between the final absolute alcohol and paraffin?
Show answer
Answer: B. It is miscible with both alcohol and paraffin
Paraffin can't infiltrate tissue that is still full of alcohol, so the clearing agent acts as the bridge. It isn't a dehydrant (A). Processing solvents are actually what remove lipids, so it can't fix them (C). Support for sectioning comes from the paraffin (D). Source: Dako/Agilent, Ch. 16, p. 148.
HT-PREP-008.
A bone biopsy needs decalcification, and preserving nuclear detail is more important than speed. Which decalcifier is the best choice?
Show answer
Answer: C. EDTA at pH 7–8
EDTA is a chelating agent: it removes calcium by binding it rather than dissolving it with strong acid. It works more slowly, but it preserves nuclear detail and nucleic acids better than prolonged acid decalcification. Mineral acids (A, D) are faster but can damage nuclear staining when exposure is excessive; formic acid (B) is milder than strong mineral acids but is still an acid decalcifier. Source: Dako, Ch. 16, p. 146.
HT-PREP-009.
A femoral head was left in a hydrochloric acid decalcifier over a long weekend without anyone checking the endpoint. On the H&E, the most likely result is:
Show answer
Answer: A. Poor nuclear staining and loss of nuclear detail
Too much time in acid damages nucleic acids. Hematoxylin then has less to bind, so nuclei look pale and smudgy. That's why the decalcification endpoint is checked and the acid washed out afterward. B requires a mercury fixative. C is the opposite of what happens. D is unrelated, since lipids are lost in processing anyway. Source: Dako/Agilent, Ch. 16, p. 146.
Embedding/Microtomy
HT-PREP-010.
A renal biopsy is submitted for a Jones (periodic acid–methenamine silver) stain of glomerular basement membranes. The recommended section thickness is about:
Show answer
Answer: A. 2 μm
Kidney biopsies are cut thin, at about 2 μm, so individual glomerular structures aren't stacked on top of each other. Routine H&E sections are usually 3–4 μm. C is closer to the range used for amyloid (see the next question). Source: Dako/Agilent, Ch. 16, pp. 147, 150.
HT-PREP-011.
Compared with routine 3–4 μm sections, Congo red sections for amyloid are commonly cut at:
Show answer
Answer: C. 8–10 μm
Amyloid deposits show up better in thicker sections than in routine ones, so labs cut Congo red sections thicker than they cut H&E. A and B are routine thickness or thinner. D is far thicker than routine paraffin methods call for. Source: Dako/Agilent, Ch. 16, pp. 147, 150.
HT-PREP-012.
A Warthin-Starry stain shows heavy brown-black background across the whole slide, including glass with no tissue on it. The sections were picked up on positively charged slides from a water bath containing adhesive. The best fix is to:
Show answer
Answer: D. Cut sections onto clean, uncoated slides with no water-bath adhesive
Silver ions are attracted to slide coatings and adhesives, so the background even reaches bare glass. That clue points to the slide, not the tissue. More silver (A) or longer development (B) makes it worse, and C hides the problem without fixing it. Source: Dako/Agilent, Ch. 16, p. 150.
HT-PREP-013.
A muscle biopsy arrives on saline-dampened gauze over wet ice for frozen-section studies. The best way to preserve morphology for cryostat sectioning is to:
Show answer
Answer: C. Orient it in OCT and snap-freeze it in isopentane chilled by liquid nitrogen
Fast freezing limits the freezing artifact that distorts muscle fibers. Slow freezing (B) and letting the tissue soak up saline (D) both create that artifact. A defeats the purpose, because these studies need unfixed frozen tissue. Source: Dako/Agilent, Ch. 16, p. 148.
Staining
HT-PREP-014.
A Congo red–stained section shows salmon-pink deposits that look apple-green under polarized light. These findings indicate:
Show answer
Answer: B. Amyloid
Apple-green birefringence under polarized light is the classic Congo red result for amyloid. Collagen (A) is naturally birefringent but doesn't give this pattern. Elastic fibers (C) are shown with stains such as Verhoeff. Glycogen (D) is a PAS target. Source: Dako/Agilent, Ch. 1, p. 19.
HT-PREP-015.
A liver biopsy shows intense magenta staining of hepatocytes with PAS. On the paired section treated with diastase before PAS, most of that staining is gone, but small round PAS-positive globules remain. What did the digestion remove?
Show answer
Answer: D. Glycogen
Diastase (alpha-amylase) digests glycogen, so glycogen staining disappears on the digested slide. Material that survives digestion is the point of running it. In liver, diastase-resistant globules are the classic finding for alpha-1 antitrypsin (C). Neutral mucins (A) and basement membranes (B) stay PAS-positive after digestion. Source: Dako/Agilent, Ch. 12, p. 112.
HT-PREP-016.
Alcian blue performed at pH 1.0 stains:
Show answer
Answer: A. Only sulfated acidic mucosubstances
At pH 2.5, Alcian blue stains both sulfated and nonsulfated acidic carbohydrates (B). At pH 1.0, only the sulfated ones stain. Neutral mucins (C) and glycogen (D) are PAS targets. Source: Dako/Agilent, Ch. 1, p. 9.
HT-PREP-017.
A skin biopsy from a patient with suspected leprosy needs an acid-fast stain. The method designed for Mycobacterium leprae is:
Show answer
Answer: C. Fite
M. leprae has a cell wall that is more easily damaged during deparaffinization. The Fite method adds peanut oil to the deparaffinizing solvent and uses a weaker acid to decolorize. Ziehl-Neelsen (A) is the standard for M. tuberculosis. Gram (B) can't get through the waxy mycobacterial wall. GMS (D) is a fungal stain. Source: Dako/Agilent, Ch. 11, p. 103.
HT-PREP-018.
In the Perls Prussian blue method, dilute hydrochloric acid releases ferric iron from tissue proteins. Which reagent then reacts with the ferric iron to form the blue product?
Show answer
Answer: A. Potassium ferrocyanide
The freed ferric ions react with potassium ferrocyanide to form insoluble ferric ferrocyanide, the bright blue pigment called Prussian blue. Hemosiderin shows as coarse blue granules. Silver nitrate (B) belongs to silver methods such as von Kossa. Sodium thiosulfate (C) removes unreduced silver. Rubeanic acid (D) isn't part of this method. Source: Dako/Agilent, Ch. 12, p. 109.
HT-PREP-019.
A lab uses a regressive hematoxylin, such as full-strength Harris. What is the purpose of the acid-alcohol step that follows it?
Show answer
Answer: B. To remove excess hematoxylin from cytoplasm and chromatin
Regressive hematoxylins overstain on purpose. A dilute acid then pulls out the excess (differentiation) until only the nuclei stay crisp. Bluing (A) comes next, in an alkaline rinse that turns the red aluminum-hematein complex blue and insoluble. The mordant (C) is the aluminum already in the hematoxylin. If differentiation is skipped or incomplete, nuclei look muddy and eosin uptake can be blocked. Source: Dako/Agilent, Ch. 2, p. 29; Ch. 13, pp. 120–121.
HT-PREP-020.
A surgeon asks for Oil Red O on a formalin-fixed, paraffin-embedded liver block to look for fat. The best response is:
Show answer
Answer: D. Explain that Oil Red O needs frozen sections because processing removes the fat
The alcohols and clearing agents used in paraffin processing dissolve neutral fats, so there's nothing left to stain. Oil Red O is done on frozen sections and mounted in a medium that won't dissolve fat. A longer staining time (A) can't bring back lost lipid. PAS-diastase (B) answers a different question. A solvent-based mounting medium (C) would dissolve fat even on a frozen section. Source: Dako/Agilent, Ch. 12, p. 112.
HT-PREP-021.
A Masson trichrome on tissue fixed only in 10% NBF is weak and dull. The most effective improvement is to:
Show answer
Answer: C. Mordant the deparaffinized sections in Bouin solution before staining
NBF alone doesn't give optimal trichrome results. Treating sections with a picric acid solution such as Bouin makes the staining stronger and brighter. A and B miss the point. Trichromes use an iron hematoxylin, such as Weigert's, because the acidic dye solutions that follow would decolorize an alum hematoxylin. The polyacid step (D) is what frees collagen to take up the fiber dye, so leaving it out ruins the result. Source: Dako/Agilent, Ch. 10, pp. 94–97; Ch. 16, p. 144.
HT-PREP-022.
On a Verhoeff–van Gieson (VVG) stain, collagen appears:
Show answer
Answer: B. Red
Verhoeff's iron hematoxylin stains elastic fibers and nuclei black (A). Van Gieson's picro-fuchsin then colors collagen red and other tissue yellow (D). Blue collagen (C) is the Masson trichrome result. Source: Dako/Agilent, Ch. 1, pp. 7, 18.
Laboratory Operations
HT-PREP-023.
Under OSHA's formaldehyde standard (29 CFR 1910.1048), which value is the short-term exposure limit (STEL)?
Show answer
Answer: C. 2 ppm over 15 minutes
The STEL is 2 ppm averaged over 15 minutes. A is the action level, which triggers extra monitoring and medical surveillance. B is the permissible exposure limit (PEL), an 8-hour time-weighted average (TWA). D isn't an OSHA formaldehyde limit. Source: OSHA, 29 CFR 1910.1048(b)–(c).
HT-PREP-024.
How much 95% ethanol do you need to make 500 mL of 70% ethanol?
Show answer
Answer: C. 368 mL
Use C₁V₁ = C₂V₂: 95% × V₁ = 70% × 500 mL, so V₁ = 35,000 ÷ 95 ≈ 368 mL. Then bring it to 500 mL with water. B (350 mL) is the trap answer: it's what you get if you treat the stock as 100% instead of 95%. A and D don't match the formula.
HT-PREP-025.
How many grams of sodium chloride (molecular weight 58.44 g/mol) do you need for 250 mL of a 0.5 M solution?
Show answer
Answer: A. 7.3 g
Grams = molarity × liters × molecular weight = 0.5 × 0.25 × 58.44 ≈ 7.3 g. B is the amount for 500 mL. C is the amount for a full liter. D is half the right answer. Convert mL to L before you multiply.
After you finish: count your correct answers by area (Fixation 5, Processing 4, Embedding/Microtomy 4, Staining 9, Laboratory Operations 3). With this few items per area, treat a miss as a pointer to a topic, not a measure of your ability. Write each miss in your error log with the reason: didn't know it, misread it, or mixed it up with something else.
What changed on November 1, 2026
ASCP's content guideline page assigns one guideline to testing dates through October 31, 2026 and a revised one to testing dates from November 1, 2026. The exam model didn't change: 100 questions, 2 hours 30 minutes, computer adaptive testing, one best answer, and the same five areas and percentage ranges. The changes are inside the outline. Compare the current guideline with the previous one.
| Area | What changed for HT | What to study now |
|---|---|---|
| Laboratory regulations | "Regulations" used to be HTL-only. "Laboratory Regulations" (e.g., CLIA, OSHA, TJC, CAP, CLSI, FDA) no longer carries that label | Quality assurance, validation of new tests/control tissue/instruments, proficiency testing and competency assessment, HIPAA, inventory, writing and reviewing procedures |
| Safety | Six short lines became a detailed outline | SDS, labeling/storage/disposal, spill response, PPE, eyewash and showers, exposure monitoring for xylene and formaldehyde (TWA, STEL, PEL), fire safety and fire classes, ergonomics, infection control and Standard Precautions |
| Lab math | "Metric system" became "Unit conversions" | Convert between units as calculations, plus percent and molar solutions |
| Fixatives | New named list of fixatives and transport media | Acetone, alcohol, Bouin, Carnoy, formalin (10% NBF, alcoholic, zinc), glutaraldehyde, Michel medium, Zamboni |
| Pathology and biochemistry | No longer marked HTL-only under Fixation and Staining tissues | Know why a stain or fixative demonstrates what it does, not just the recipe |
| Immunohistochemistry | HT used to include basic antigen retrieval and IHC staining theory. Now HT covers IHC/IF terminology plus fixation and processing; staining theory, antigen retrieval techniques, control selection, antibody preparation and detection theory are HTL-only | Learn the vocabulary and how fixation and processing affect IHC. Don't over-study detection chemistry |
| Enzyme histochemistry and ISH | Fixation and processing questions on both exams; staining questions on these are HTL-only | Specimen handling, not staining procedures |
| Processing | "Calcified/decalcified tissue" became "Decalcification," and "special stains" was added | Link processing choices to how special stains turn out |
| Staining | "Function" removed; HTL-only "preliminary screening of special stains" removed; Hall bile stain added | Add Hall stain to your stain list |
| Mounting and equipment | Coverslipping now names manual and automated methods. Equipment examples now include whole slide imager, pipette, balance and reagent recycler | Basic use, maintenance and troubleshooting of each |
Older study materials still cover most of what's tested, because the five areas and their weights didn't change. The gaps to fill are regulations, detailed safety, the named fixatives, Hall stain, and IHC vocabulary.
Your 4-week HT study plan
Time assumption: about 45–90 focused minutes on most days. That's our editorial starting point for someone who already works in or trained in a histology lab, not an ASCP requirement. Keep every area in rotation every week, even when the focus is elsewhere.
| Week | Focus | Study tasks | Practice | End-of-week check |
|---|---|---|---|---|
| 1 | Fixation + processing | Learn the fixative table and the processing steps. Fixation parameters, pigments, decalcification and endpoints | Redo HT-PREP-001 to 009 cold; explain each answer out loud | Can you name the fixative or transport medium for urate crystals, EM, immunofluorescence and trichrome mordanting? |
| 2 | Embedding/microtomy | Orientation, section thickness by stain, frozen sections, slide coatings, instrument maintenance | Redo HT-PREP-010 to 013; write your own question for each instrument | Can you match each special stain to its usual section thickness? |
| 3 | Staining | Work through the stain table one row a day per group; IHC/IF vocabulary; mounting | Redo HT-PREP-014 to 022; cover the result column of the stain table and recall it | For each stain: what does it show, what color, and what makes it fail? |
| 4 | Lab operations + mixed review | Safety checklist, OSHA formaldehyde limits, regulations terms, worked math | Redo HT-PREP-023 to 025, then all 25 in random order; clear your error log | Every error-log entry re-explained without notes |
Other timelines:
- 2 weeks: combine Weeks 1 and 2, then Weeks 3 and 4. Do a short mixed review every day, and don't drop the low-weight areas.
- 6 weeks: spread Staining over two weeks, give Lab Operations its own week, and keep the last week for mixed review.
- 8 weeks: split each week above into two, and add a weekly mixed retrieval session covering earlier weeks.
If you've already failed once: ASCP's score report for a failed exam breaks your score down by content area (ASCP Examination Results). Build your plan around your two weakest areas, and keep the rest on review.
How to study each HT content area
Fixation
Fixatives stop autolysis and stabilize tissue. They work by cross-linking proteins (formaldehyde, for example) or by coagulating them (alcohols, picric acid). Most exam questions turn on matching the fixative to the job and spotting what went wrong. Know the variables ASCP lists: specimen size, fixative volume, time, temperature and pH.
| Fixative or medium | What it is | Typical use | Watch for |
|---|---|---|---|
| 10% NBF | About 4% formaldehyde, buffered near pH 7.2–7.4 | Routine histology | Cross-links slowly; use about 20:1 volume and 3–4 mm slices; prolonged fixation can alter antigen accessibility |
| Alcoholic formalin | Formalin with alcohol (alcohol–formalin–acetic acid mixtures are common) | Combines formaldehyde fixation with alcohol; appears as a fixation step in some processor schedules | Alcohol extracts lipids |
| Zinc formalin | Formaldehyde with zinc salts | Less toxic alternative to mercury-containing fixatives | Formulations vary; follow the lab's procedure |
| Bouin | Formaldehyde, acetic acid and picric acid | Good morphology; used as a trichrome mordant after NBF | Tissue turns yellow; long storage damages DNA and RNA; wash well |
| Carnoy | Ethanol, chloroform, acetic acid (60:30:10) | Non-aqueous coagulant; tissue is nearly dehydrated already, so processing is shorter | Contains chloroform |
| Alcohol | Ethanol or methanol | Smears and cytology; urate crystals | Distorts solid tissue when used alone |
| Acetone | Organic solvent | Some smear and frozen-section protocols (e.g., a citrate–acetone fixative for TRAP smears) | Not a routine tissue fixative |
| Glutaraldehyde | Buffered dialdehyde | Electron microscopy, usually followed by osmium tetroxide | EM portions are usually handled by EM specialists |
| Michel medium | Transport medium | Holding biopsies for direct immunofluorescence when snap-freezing isn't possible | Not a routine fixative |
| Zamboni | Paraformaldehyde with picric acid | Specialized studies, e.g., skin punch biopsies for nerve fiber evaluation | Paraformaldehyde must be handled with caution |
Sources: Dako/Agilent, Ch. 16, pp. 141–148; ARUP Laboratories, Direct Immunofluorescence Tissue Biopsy specimen requirements (Michel); Khoshnoodi et al., 2021 (Zamboni). The list itself comes from the ASCP guideline, p. 5.
Pigment to know: mercury-containing fixatives such as B5 leave a brown crystalline mercury pigment throughout the tissue. It is removed with iodine followed by sodium thiosulfate before staining, and mercury waste falls under toxic waste rules (Dako/Agilent, Ch. 16, p. 145).
Processing
The sequence is always dehydration (alcohols), clearing (xylene or a substitute), then paraffin infiltration. Small needle biopsies and bloody specimens need gentler schedules; fatty specimens can run longer (Dako/Agilent, Ch. 16, p. 148).
For decalcification, compare the two families:
| Acid decalcifiers (HCl, nitric, formic) | EDTA (chelating) | |
|---|---|---|
| Speed | Days | Weeks |
| Nuclear and nucleic acid preservation | Damaged by long exposure | Preserved |
| Best when | Speed matters and endpoint is monitored | DNA, RNA or enzyme methods may follow |
Source: Dako/Agilent, Ch. 16, p. 146.
Embedding and microtomy
Orientation matters most for specimens such as skin, small GI biopsies and vas deferens (Dako/Agilent, Ch. 16, p. 150). Section thickness is a common exam angle:
| Section | Typical thickness |
|---|---|
| Routine H&E | 3–4 μm |
| Kidney biopsy (e.g., Jones) | About 2 μm |
| Congo red for amyloid | 8–10 μm (some sources say up to 12) |
Source: Dako/Agilent, Ch. 16, pp. 146–147, 150.
Two practical rules come up often. First, silver stains on charged or adhesive-coated slides can produce background everywhere, so use clean uncoated slides. Second, unfixed tissue for frozen studies should be snap-frozen fast, not left to freeze slowly or soak up saline.
Staining
Staining is the biggest area. Learn it by target, not alphabetically. For each stain, know what it shows, the expected color, and one way it fails.
| Target | Stain | Typical positive result |
|---|---|---|
| Nuclei and cytoplasm | H&E | Nuclei blue to purple; cytoplasm pink |
| Carbohydrates | PAS | Glycogen, neutral mucins, basement membranes magenta; diastase removes glycogen |
| Carbohydrates | Alcian blue pH 2.5 / pH 1.0 | Acidic mucins blue; at pH 1.0 only sulfated |
| Carbohydrates | Mucicarmine | Mucins rose to red; also the Cryptococcus capsule |
| Amyloid | Congo red | Salmon-pink; apple-green birefringence under polarized light |
| Connective tissue | Masson trichrome | Collagen blue or green; muscle and cytoplasm red; nuclei black |
| Connective tissue | Verhoeff–van Gieson | Elastic fibers black; collagen red; other tissue yellow |
| Connective tissue | Reticulin (silver) | Reticulin fibers black |
| Microorganisms | Ziehl-Neelsen / Kinyoun / Fite | Acid-fast bacilli red-pink on blue; Fite for M. leprae |
| Microorganisms | Gram | Gram-positive blue-purple; Gram-negative pink |
| Microorganisms | GMS | Fungi black on green |
| Microorganisms | Warthin-Starry / Steiner | Spirochetes and H. pylori black on yellow |
| Microorganisms | Giemsa | H. pylori, protozoa and other organisms |
| Pigments and minerals | Perls Prussian blue | Ferric iron (hemosiderin) blue |
| Pigments and minerals | Fontana-Masson | Melanin and other silver-reducing substances black |
| Pigments and minerals | von Kossa | Calcium deposits black |
| Pigments and minerals | Rhodanine | Copper bright orange to brown |
| Pigments and minerals | Hall | Bile pigment (bilirubin) |
| Lipids | Oil Red O | Neutral fats orange-red; frozen sections only |
| Nerve | Luxol fast blue | Myelin |
| Cells | Toluidine blue | Mast cell granules metachromatic purple |
Sources: Dako/Agilent, Ch. 1, pp. 5–19; Ch. 11, pp. 99–104; Ch. 12, pp. 107–115; Ch. 18, p. 164; Ch. 19, p. 167. The stain names come from the ASCP summary of stains, pp. 5–6.
H&E basics that get tested: a progressive hematoxylin stains to the right intensity and stops. A regressive one overstains and needs differentiation in acid alcohol. Bluing in an alkaline rinse then turns nuclei from red to blue (Dako/Agilent, Ch. 13, pp. 120–121).
Why controls matter: a negative special stain with no control can't tell you whether the substance is absent or the stain failed. That's why special stains are run with control material (Dako/Agilent, Ch. 1, p. 4).
Laboratory operations
Safety checklist from the current guideline: SDS, labeling, storage and disposal, spill response, health hazards, PPE, eyewash stations and showers, exposure monitoring, fire safety, ergonomics, infection control, Standard Precautions, disinfection and hand hygiene (ASCP guideline, pp. 3–4).
OSHA formaldehyde limits (29 CFR 1910.1048):
| Limit | Value |
|---|---|
| Action level | 0.5 ppm, 8-hour TWA |
| Permissible exposure limit (PEL) | 0.75 ppm, 8-hour TWA |
| Short-term exposure limit (STEL) | 2 ppm, 15 minutes |
Worked example 1: a percent solution. To make 1 L of 0.5% HCl in 70% ethanol (an acid alcohol differentiator): 0.5% of 1,000 mL = 5 mL. Add 5 mL concentrated HCl to 995 mL of 70% ethanol (Dako/Agilent, Ch. 13, p. 125).
Worked example 2: a unit conversion. 1 mm = 1,000 μm, so a 4 μm section is 4 ÷ 1,000 = 0.004 mm. Going the other way, a 0.002 mm kidney section is 0.002 × 1,000 = 2 μm.
HT exam at a glance
| Item | Detail |
|---|---|
| Credential | Histotechnician, HT(ASCP) |
| Exam owner | ASCP Board of Certification (ASCP BOC) |
| Where | Pearson testing centers |
| Format | 100 multiple-choice questions, four options, one best answer |
| Time | 2 hours 30 minutes |
| Method | Computer adaptive testing (CAT); questions from all areas appear throughout |
| Skipping | You must answer each question before moving on; you can flag questions and review them if time remains |
| Calculator | On-screen calculator provided |
| Unscored items | Field-test questions are mixed in and look the same as scored ones |
| Scoring | Scaled score from 100 to 999; minimum passing score 400 |
| Results | Preliminary pass/fail on screen; an email to view your official score report within four business days, once transcripts are processed |
| Application fee | $235, nonrefundable |
Sources: ASCP About the Examination; ASCP Examination Results; ASCP HT credential page.
How to use practice questions for a CAT exam
On a CAT exam, a right answer brings a slightly harder question and a wrong answer brings a slightly easier one. Your score reflects the whole pattern of answers. There's no fixed number or percentage you need to get right, and ASCP warns that missing questions on purpose to get easier ones backfires (ASCP About the Examination). That's why a percentage on practice questions can't be converted into an ASCP score. Use practice like this instead:
- Log every miss by content area and by why you missed it.
- Re-learn the principle behind the miss, not just the answer.
- Redo the same items a few days later, in a different order.
- Answer every question as you go, without skipping, because the real exam won't let you skip.
- Use timed blocks to practice pacing, not to predict your result. At 150 minutes for 100 questions, that's about 90 seconds per question.
Final-week checklist
- Open the current ASCP guideline and confirm you've touched every line in it at least once.
- Clear your error log: re-explain every entry without notes.
- Rehearse the stain and fixative tables from memory rather than rereading them.
- Do short mixed timed sets.
- Re-run the lab math and the safety and regulation terms.
- Skip "exact exam question" lists online. They're unreliable, and they don't replace understanding the principles.
- Check your test-center details using the instructions from ASCP and Pearson.
Who can take the HT(ASCP) exam
You must meet one eligibility route before you apply, and ASCP decides eligibility only after receiving a paid application (ASCP Application Policies). Here are the U.S. routes (ASCP HT credential page):
- Route 1: You completed a NAACLS-accredited histotechnician program within the last 5 years.
- Route 2: You have 60 semester hours (90 quarter hours) or an associate degree from an accredited college or university, including 12 semester hours of biology and chemistry combined (both required). Within the last 5 years, you also have one of the following: 1 year of full-time clinical histopathology experience; 1 year of full-time veterinary, industry or research histopathology experience in the U.S. or Canada; or a structured histology program of at least 9 months with at least 480 clinical hours. Your experience must cover all five areas.
- Route 3: You have the same academic credit as Route 2, plus a 50-week U.S. military histotechnician course completed within the last 10 years.
International candidates apply for HT(ASCPi), which has separate routes. Check yours with ASCP's Eligibility Assistant, then see ASCP exam registration for the application steps.
Common questions
Is the HT exam the same as the HTL exam? No. They share one guideline with the same five areas and percentages, but some topics are marked HTL-only. These include IHC staining theory, antigen retrieval techniques, detection theory, staining for enzyme histochemistry and ISH, management and education principles, preparation for molecular testing, and refractive index (ASCP guideline, pp. 2–4). ASCP now titles HTL "Scientist in Histotechnology."
What does ASCP recommend reading? ASCP's HT/HTL suggested reading list was reviewed in June 2026. ASCP says it is only a partial reference and that exam content isn't drawn solely from it. Several titles are flagged as more appropriate for the HTL level, so HT candidates don't need to buy or read everything on it.
What if I don't pass? Your score report will show your results by content area. See ASCP exam results for how to read it and ASCP BOC's After the Examination page for current reapplication rules.
How do I keep the credential? Through ASCP's Credential Maintenance Program. See ASCP BOC's Maintain Your Credentials page.
Sources
Last verified: November 2, 2026. We checked the content guideline and its date boundary, exam format and scoring, results timing, eligibility routes and fee, the reading list, and the OSHA formaldehyde limits against the sources below.
- ASCP BOC. HT/HTL Examination Content Guideline, valid for testing dates beginning November 1, 2026. Revised July 10, 2026; pp. 1–6.
- ASCP BOC. HT/HTL Examination Content Guideline, valid for testing dates up to and including October 31, 2026. Revised July 10, 2026; pp. 1–5.
- ASCP BOC. Histotechnician – HT Content Guideline (date selector).
- ASCP BOC. Histotechnician – HT credential page.
- ASCP BOC. About the Examination.
- ASCP BOC. Examination Results.
- ASCP BOC. Application Policies.
- ASCP BOC. HT/HTL Suggested Reading. Reviewed June 2026.
- Kumar GL, Kiernan JA (eds.). Education Guide: Special Stains and H&E, 2nd ed. Dako, 2010; accessible copy hosted by the University of Basel.
- OSHA. Formaldehyde, 29 CFR 1910.1048, paragraphs (b) and (c).
- ARUP Laboratories. Direct Immunofluorescence, Tissue Biopsy — specimen requirements. Effective January 21, 2025.
- Khoshnoodi MA et al. Intraepidermal Nerve Fiber Density as Measured by Skin Punch Biopsy as a Marker for Small Fiber Neuropathy. Diagnostics, 2021.
Castleport Test Prep is an independent exam prep publisher. We are not affiliated with, endorsed by, or approved by the American Society for Clinical Pathology (ASCP) or the ASCP Board of Certification. HT(ASCP), HTL(ASCP) and other credential names are used only to identify the exams discussed; trademarks belong to their respective owners. The practice questions on this page are original and are not official exam questions. Passing is not guaranteed.
By the Castleport Test Prep Editorial Team.