Clinical Education Center
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- ABL Kinase Domain Mutation in CML, Cell-based
- ABO Group and Rh Type
- Acid-Fast Bacillus (AFB) Identification, Sequencing and Stain, Paraffin Block
- ADAMTS13 Activity with Reflex to ADAMTS13 Inhibitor
- Alcohol Metabolites, Quantitative, Urine
- Alpha-Globin Common Mutation Analysis
- Alpha-Globin Gene Deletion or Duplication
- Alpha-Globin Gene Sequencing
- Anti-Müllerian Hormone AssessR™
- Anti-PF4 and Serotonin Release Assay (SRA) for Diagnosing Heparin-induced Thrombocytopenia/Thrombosis (HIT/HITT)
- Antiphospholipid Antibodies
- ASCVD Risk Panel with Score
- Autoimmune Epilepsy Evaluation
- Autoimmune Diseases, Tests for
- B-cell and T-cell Clonality Assays by PCR
- B-Type Natriuretic Peptide (BNP)
- BCR-ABL1 Gene Rearrangement, Quantitative PCR
- Beta-Globin Complete
- BRCAvantage®, Ashkenazi Jewish Screen
- BRCAvantage®, Rearrangements
- BRCAvantage™, Comprehensive
- BRCAvantage™, Single Site
- CDH1 Sequencing and Deletion/Duplication
- Clostridium difficile Diagnostic Testing
- C1 Inhibitor, Protein and Functional Tests
- Calreticulin (CALR) Mutation Analysis
- Carbapenem Resistant Enterobacteriaceae Culture Screen
- Cardio IQ Lipoprotein Fractionation, Ion Mobility
- Cervical Cancer, TERC, FISH
- CFvantage® Cystic Fibrosis Expanded Screen
- Chlamydia trachomatis, TMA
- Chlamydia trachomatis/Neisseria gonorrhoeae RNA, TMA
- Chromosomal Microarray, POC, ClariSure®, Oligo-SNP
- Chromosomal Microarray, Postnatal, ClariSure® Oligo-SNP
- Chromosome Analysis and AFP with Reflex to AChE, Fetal Hgb, Amniotic Fluid
- Chromosome Analysis, Amniotic Fluid
- Chromosome Analysis, Blood
- Chromosome Analysis, Blood with Reflex to Postnatal, ClariSure® Oligo-SNP Array
- Chromosome Analysis, Chorionic Villus Sample
- Chromosome Analysis, High Resolution
- Chromosome Analysis, High Resolution with Reflex to Postnatal, ClariSure® Oligo-SNP Array
- Chromosome Analysis, Mosaicism
- Chromosome Analysis, Neonatal Blood
- Chromosome Analysis, Sister Chromatid Exchange
- Chromosome Analysis, Tissue
- Chromosome DEB Assay for Fanconi anemia
- Chronic Lymphocytic Leukemia (CLL) - Diagnostic and Prognostic Testing
- Culture, Fungus
- Culture, Urine, Routine
- Cystic Fibrosis Screen
- Cytomegalovirus (CMV) and Epstein Barr Virus (EBV) PCR
- D-Dimer, Quantitative
- Dementia, Secondary Causes
- Dengue Virus Testing
- Diabetes Risk Panel with Score and Cardio IQ® Diabetes Risk Panel with Score
- Drug Testing, General Toxicology (Blood, Urine, or Serum)
- Drug Toxicology Alcohol Metab, QN, Oral Fluid
- Drug Toxicology Monitoring, Oral Fluid Testing
- Factor V (Leiden) Mutation Analysis
- Familial Mediterranean Fever Mutation Analysis
- First Trimester Screen, hCG
- First Trimester Screen, Hyperglycosylated hCG (h-hCG)
- FISH, Angelman
- FISH, MET Amplification
- FISH, Myeloma, 17p-, rea 14q32 with Reflexes
- FISH, Prader-Willi
- FISH, Prenatal Screen
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- HCV Genotyping
- Helicobacter pylori (H pylori) Antibody Discontinuation
- Heparin, Anti-Xa
- Hepatitis B Surface Antibody, Quantitative
- Hepatitis C Antibody with Reflex to HCV RNA, PCR with Reflex to Genotype
- Hepatitis C Viral RNA Genotype 1 NS5A Drug-resistance
- Hepatitis C Viral RNA Genotype 3 NS5A Drug Resistance
- Hepatitis C Viral RNA NS3 Drug Resistance
- Hepatitis C, RNA, Quantitative, PCR
- Hereditary Cancer Panels: MYvantageTM Hereditary Comprehensive Cancer Panel and GIvantageTM Hereditary Colorectal Cancer Panel
- Hereditary Hemochromatosis DNA Mutation Analysis
- Herpes Simplex Virus (HSV) Type-Specific IgG Antibodies
- Herpes Simplex Virus Type 2 (HSV-2) IgG Inhibition, ELISA
- HIV-1 Coreceptor Tropism, Proviral DNA
- HIV-1 Coreceptor Tropism, Ultradeep Sequencing
- HIV-1 Integrase Genotype
- HIV-1/2 Antigen and Antibodies, Fourth Generation, with Reflexes
- HPV mRNA E6/E7
- Influenza A and B Antigen, Immunoassay
- Influenza Type A and B Antibodies
- Insulin, Intact, LC/MS/MS
- Integrated Screen, Part 1
- Integrated Screen, Part 2
- Intrinsic Factor Blocking Antibody
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- Maternal Serum AFP
- Melanoma, BRAF V600E and V600K Mutation Analysis, THxID®
- Metanephrines, Fractionated, Free, LC/MS/MS, Plasma
- Methylenetetrahydrofolate Reductase (MTHFR), DNA Analysis
- Microalbumin (Urinary Albumin Excretion)
- Pain Management and CYP2D6/CYP2C19
- Pain Management, Naltrexone, Quantitative, Urine
- Partial Thromboplastin Time, Activated (aPTT)
- Penta Screen
- PIK3CA Mutation Analysis
- PNH with FLAER (High Sensitivity)
- Prothrombin Time with INR
- PTH, Intact and Calcium
- Streptococcus pneumoniae (Pneumococcal) Antibody Tests
- Saccharomyces cerevisiae Antibodies (ASCA) (IgG, IgA)
- Sequential Integrated Screen, Part 1
- Sequential Integrated Screen, Part 2
- Serum Integrated Screen, Part 1
- Serum Integrated Screen, Part 2
- Serum Pregnancy Tests
- Sickle Cell Screen
- Stepwise, Part 1
- Stepwise, Part 2
- SureSwab® Trichomonas vaginalis RNA, Qualitative TMA
- SureSwab®, Candidiasis, PCR
- TP53 Sequencing and Deletion/Duplication
- T4, Free
- Tamoxifen and Metabolites, LC-MS/MS
- Testosterone Testing
- Total Testosterone, LC/MS/MS
- Triple Screen
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- No FAQs found
- No FAQs found
Hepatitis C Antibody with Reflex to HCV RNA, PCR with Reflex to GenotypeTest code(s) 94345
Question 1. Why reflex from a positive HCV antibody test result to quantitative HCV RNA and (if HCV RNA >300 IU/mL) to HCV genotype?
The reflex algorithm allows 3 important HCV tests to be completed, if necessary, with a single blood draw. Each of the 3 tests provides information that is important when a patient enters care.1
- HCV antibody testing is the initial screening test. A positive result is consistent with prior resolved infection, active infection, or a false-positive antibody, but a supplemental test is needed to confirm active infection.
- The reflex to quantitative HCV RNA testing serves 2 important functions: 1) as a supplemental test to confirm active infection in patients with a positive HCV Ab result; and 2) to establish the baseline viral load (concentration of HCV virus in blood). Knowing the viral load at baseline helps physicians monitor response to therapy.
- HCV genotype testing is used to inform treatment decisions and duration of therapy.
The tests included in this reflex panel are recommended to guide the selection (and, for some patients, duration) of antiviral treatment.1 However, only about half of patients have had confirmatory HCV testing by the time of their first visit to an HCV treatment provider, and an even lower proportion have had quantitative RNA and genotype results.2 The reflex approach should improve the proportion of patients who have this complete series of important HCV assay results.
Question 2. Why are HCV RNA results being reported in IU/mL?
Results are reported in international units per milliliter (IU/mL) to facilitate comparisons between results generated by different test methods. This is important because the various methods used by different laboratories are not standardized against each other. Use of IU/mL reporting units helps to make the comparison of viral load results across different methods more reliable.
Question 3. Why does Quest Diagnostics also report results as log IU/mL?
This makes it easier to understand whether a change in viral load is clinically meaningful.
Replicate PCR test results using the same specimen can vary analytically by as much as 0.5 log IU/mL; thus, only changes greater than 0.5 log IU/mL from one measurement to the next (or across several measurements) are considered to represent true changes in viral load.3 Reporting the viral load results in log IU/mL units helps the healthcare provider accurately interpret changes in viral load and better assess a patient's response to antiviral treatment.
Question 4. What do these test results mean: “<15 Detected” and “<15 Not Detected”?
A “<15 Detected” viral load result means the assay detected HCV RNA in the patient’s specimen at a very low level (<15 IU/mL), but could not measure the precise level. A “<15 Not Detected” viral load result means the assay did not detect HCV RNA in the patient’s specimen.
This test is performed using a Taqman® assay. The lowest viral load this assay can accurately quantify is 15 IU/mL, but the qualitative limit of detection is in the 10 to 13 IU/mL range. Therefore, even when the viral load is below 15 IU/mL, we can still report qualitative detection of HCV RNA consistent with active infection in some cases.
Question 5. Which HCV genotypes may be reported by the LiPA assay at Quest Diagnostics?
The LiPA genotype assay can identify all 6 major HCV genotypes (1–6). In many cases, it can also differentiate among HCV subtypes, including 1a, 1b, 2a-c, 3a, 3b, 3c, 3k, 4a/c/d, 4f, 4h, 5a, 6a/b, and 6c-l. However, if the LiPA banding pattern for a patient specimen does not sufficiently differentiate between subtypes, only the genotype may be reported (for example, "genotype 1" or "genotype 2").
Question 6. Why didn’t the test reflex to HCV genotype when my patient had a detectable viral load?
The LiPA usually requires a minimum viral load of 300 IU/mL to successfully obtain a genotype. Since the viral load assay used in this reflex test has a much lower limit of quantitation, it is possible for the patient to have a detectable viral load (below 300 IU/mL) and not have a reportable genotype result. Therefore, this test code does not reflex to HCV genotype if the patient’s viral load is <300 IU/mL.
Question 7. The test result is "1a" with the comment, "We cannot rule out genotype 6 subtypes c-I." Does that mean the patient is coinfected?
Not necessarily. The HCV genotype assay is performed by analyzing LiPA banding patterns that are indicative of the genotype. Two regions of the genome are assessed: the 5' UTR and the core region. Genotype 6 subtypes c-l have the same LiPA banding pattern as genotype 1 when this technique is performed. Therefore, the core region is used to differentiate type 1 from type 6. If the core region LiPA banding pattern is not conclusive, we report a result of “HCV genotype 1 but cannot rule out type 6 subtypes c-l.”
Question 8. What is the interpretation of the following LiPA test result: “Hybridization pattern is consistent with the following genotypes: 1a and 2b”?
This result means that the specimen produced a LiPA banding pattern indicating that HCV subtypes 1a and 2b were both present. This test result is consistent with HCV coinfection by both subtypes.
Question 9. How does the HCV genotype (LiPA) test differ from the HCV NS3, NS5a, and NS5b tests for drug resistance?
The LiPA genotype test is designed to identify all 6 major HCV genotypes. In contrast, the NS3, NS5a, and NS5b drug resistance tests detect mutations associated with drug resistance for a particular HCV genotype. They are not intended for determining HCV genotype and subtype. Separate test codes for drug resistance testing are available, depending on the HCV genotype and the gene of interest:
- Hepatitis C Viral RNA Genotype 1 NS3 Drug Resistance (test code 90924)
- Hepatitis C Viral RNA Genotype 1 NS5a Drug Resistance(test code 92447)
- Hepatitis C Viral RNA Genotype 1 NS5b Drug Resistance(test code 92204)
- Hepatitis C Viral RNA Genotype 3 NS5a Drug Resistance(test code 93325)
The HCV genotype (LiPa) test should be performed before ordering an applicable HCV drug resistance test.
- AASLD-IDSA. HCV testing and linkage to care. Recommendations for testing, managing, and treating hepatitis C. http://www.hcvguidelines.org/full-report/hcv-testing-and-linkage-care. Updated July 6, 2016. Accessed February 3, 2017.
- Holmberg SD, Spradling PR, Moorman AC, et al. Hepatitis C in the United States. N Engl J Med. 2013;368:1859-1861.
- Kleiber J, Walter T, Haberhausen G, et al. Performance characteristics of a quantitative, homogeneous TaqMan RT-PCR test for HCV RNA. J Mol Diagn. 2000;2:158-166.