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Citrate buffer used for HIER typically has a pH of:

3.0

9.0

6.0

7.4

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Key Facts: QIHC Exam

Total Items

ASCP BOC

90 min

Exam Time

ASCP

$260

Exam Fee

ASCP

6 mo

Required Experience

IHC in last 5 years

The ASCP QIHC (Qualification in Immunohistochemistry) is a 50-item, 90-minute, $260 qualification exam. Eligibility: 6 months IHC experience in last 5 years. Master HIER (citrate pH 6.0, EDTA pH 8-9), DAB detection, common IHC marker panels (lung TTF-1+/p40+; lymphoma CD20/CD3/CD30; melanoma S100/SOX10), and CAP validation rules (≥10 positive + ≥10 negative for predictive markers).

Sample QIHC Practice Questions

Try these sample questions to test your QIHC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the gold-standard fixative for routine immunohistochemistry?

A.10% neutral buffered formalin

B.Bouin's solution

C.Zenker's fixative

D.95% ethanol

Explanation: 10% neutral buffered formalin (NBF) is the universally accepted fixative for IHC. It cross-links proteins via methylene bridges, preserves morphology, and is compatible with virtually all validated antibody clones and antigen retrieval protocols.

2What is the recommended fixation time range for most diagnostic IHC, particularly breast biomarkers?

A.1-2 hours

B.6-72 hours (24-48 hours optimal)

C.Minimum 7 days

D.Less than 4 hours

Explanation: ASCO/CAP and CAP IHC guidelines specify 6-72 hours of 10% NBF fixation for breast biomarker testing (HER2, ER, PR), with 24-48 hours considered optimal. Cold ischemic time should be under 1 hour.

3Cold ischemia time refers to:

A.Time tissue is held at 4°C before processing

B.Time from tissue removal to placement in fixative

C.Time tissue spends in formalin before processing

D.Time from sectioning to staining

Explanation: Cold ischemia time is the interval between surgical removal (devascularization) of tissue and immersion in fixative. Prolonged cold ischemia (>1 hour) degrades labile antigens such as phospho-proteins and hormone receptors.

4Which clearing agent is most commonly used during routine paraffin tissue processing?

A.Acetone

B.Xylene

C.Methanol

D.Glycerin

Explanation: Xylene is the standard clearing agent because it is miscible with both ethanol and paraffin, allowing displacement of dehydrant before paraffin infiltration.

5Standard section thickness for IHC is:

A.1-2 μm

B.3-5 μm

C.8-10 μm

D.15-20 μm

Explanation: Sections of 3-5 μm (typically 4 μm) provide a single cell-layer thickness that maximizes antibody penetration and morphologic detail for IHC.

6Which slide type is preferred for IHC to ensure tissue adhesion through retrieval and washes?

A.Plain glass slides

B.Frosted slides without coating

C.Positively charged (silanized) slides

D.Albumin-coated slides only

Explanation: Positively charged slides electrostatically bind the negatively charged tissue, preventing detachment during high-temperature antigen retrieval and aggressive wash steps.

7What temperature range is optimal for the flotation water bath when picking up paraffin sections for IHC?

A.20-25°C

B.40-45°C

C.55-60°C

D.75-80°C

Explanation: A water bath of 40-45°C (a few degrees below the paraffin melting point) flattens sections without overheating, which would denature heat-labile antigens and increase background.

8The chemical mechanism of formalin fixation is:

A.Coagulation of proteins by alcohol bridges

B.Formation of methylene cross-links between amino groups

C.Precipitation by mercuric chloride

D.Oxidation of cysteine residues

Explanation: Formaldehyde reacts with primary amines (lysine, arginine) and other nucleophilic side chains to form methylene (-CH2-) cross-links, stabilizing protein architecture but masking many epitopes.

9Heat-induced epitope retrieval (HIER) primarily reverses:

A.Tissue autolysis

B.Methylene bridges formed by formalin cross-linking

C.Endogenous peroxidase activity

D.Lipid masking

Explanation: HIER hydrolyzes formalin-induced methylene cross-links and refolds antigens, restoring epitope accessibility. Buffer pH and temperature determine effectiveness.

10Citrate buffer used for HIER typically has a pH of:

A.3.0

B.6.0

C.7.4

D.9.0

Explanation: Citrate buffer pH 6.0 is a low-pH HIER buffer effective for many antigens (e.g., CK7, CD20, vimentin). EDTA/Tris pH 9.0 is the high-pH alternative.

About the QIHC Exam

ASCP BOC Qualification credential for histology professionals performing immunohistochemistry. Validates working knowledge of IHC fundamentals (formalin fixation, antigen retrieval HIER vs enzymatic), detection systems (DAB chromogen, polymer-based UltraView/EnVision), common diagnostic IHC marker panels (CK7/CK20, lymphoma markers, melanoma S100/SOX10), predictive markers (HER2, ER/PR, PD-L1, MMR), QC and validation per CAP guidelines, and troubleshooting.

Questions

50 scored questions

Time Limit

90 minutes

Passing Score

Scaled

Exam Fee

$260 (ASCP BOC)

QIHC Exam Content Outline

20%

Tissue Fixation, Processing, Antigen Retrieval

10% NBF, fixation timing, HIER vs enzymatic, decalcification effects

20%

Detection Systems & Chromogens

ABC, polymer (UltraView, EnVision), DAB vs AEC, counterstain

25%

Common IHC Antibody Panels

CK7/CK20, lung (TTF-1, p40), breast (ER/PR/HER2), lymphoma, melanoma, prostate, MMR

15%

Predictive Markers

HER2 0/1+/2+/3+ scoring, ER/PR Allred or %, PD-L1 (TPS, CPS), Ki-67

10%

QC, Validation & Troubleshooting

CAP validation rules, controls, lot QC, artifact troubleshooting

10%

Lab Operations, Compliance, Safety

CAP/CLIA, automation (Ventana, Leica, Dako), formalin/xylene safety

How to Pass the QIHC Exam

What You Need to Know

Passing score: Scaled
Exam length: 50 questions
Time limit: 90 minutes
Exam fee: $260

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

QIHC Study Tips from Top Performers

1Master CK7/CK20 patterns: lung adeno (CK7+/CK20-), colon (CK7-/CK20+), urothelial (CK7+/CK20+), HCC (CK7-/CK20-)

2Memorize HER2 IHC scoring: 0/1+/2+/3+; 2+ requires reflex FISH; 3+ POSITIVE

3Know lymphoma panels: B-cell CD20/PAX5/CD79a; T-cell CD3/CD2/CD5/CD7; Hodgkin CD30+CD15+ Reed-Sternberg

4Apply Lynch screen: MMR proteins MLH1/MSH2/MSH6/PMS2 — paired loss patterns (MLH1+PMS2 lost, or MSH2+MSH6 lost)

5Know PD-L1 clones by drug: 22C3 (pembrolizumab), 28-8 (nivolumab), SP142 (atezolizumab), SP263 (durvalumab/pembrolizumab)

Frequently Asked Questions

What antigen retrieval should I use?

HIER (heat-induced epitope retrieval) is most common: citrate buffer pH 6.0 (broad use); EDTA pH 8.0/9.0 (targets formaldehyde-cross-linked epitopes especially nuclear); pressure cooker, microwave, or water bath. Enzymatic retrieval (proteinase K, trypsin) for select antibodies. Manufacturer datasheet specifies optimal method per antibody.

How is HER2 IHC scored?

ASCO/CAP scoring 0/1+/2+/3+ for breast cancer HER2: 0 = no staining; 1+ = faint incomplete membrane <10% cells; 2+ = weak-moderate complete membrane >10% cells (EQUIVOCAL — reflex to FISH); 3+ = strong complete membrane >10% cells (POSITIVE). For gastric: similar but adjusted for tumor heterogeneity.

What is CAP validation for IHC?

Per CAP guidelines: non-predictive markers require ≥20 positive + ≥20 negative tissues for new antibody validation, with ≥90% concordance. Predictive markers (HER2, ER/PR, PD-L1) require ≥40+/40 (initially proposed; check current guideline). New lot of validated antibody requires 1 positive + 1 negative tissue verification.

How should I study for ASCP QIHC?

Plan 30-50 hours over 4-6 weeks. Focus on common IHC marker panels (25%) and detection systems (20%). Master CK7/CK20 patterns by anatomic origin, lung adenocarcinoma vs squamous (TTF-1/Napsin A vs p40), HER2 scoring, MMR/MSI panel (MLH1/MSH2/MSH6/PMS2), and PD-L1 clones (22C3, 28-8, SP142, SP263).