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Hepatitis C, RNA, Quantitative, PCR
Test code(s) 35645


The FAQ information attached by the previously provided link has been retired. The link continues to be available for your historic reference. Current FAQs can be viewed at QuestDiagnostics.com/FAQs.

Question 1. Why are HCV results being reported in IU/mL? What is log IU/mL?

IU/mL is the abbreviation for international units per milliliter. Results are reported in IU/mL units to facilitate comparisons between results generated by available test methods. This is important because the various methods are not standardized. Use of IU/mL helps standardize viral load test results.

We also report the viral load in log IU/mL units. PCR test results on the same sample can vary as much as 0.5 log IU/mL; thus, only changes greater than 0.5 log IU/mL are clinically significant.

Reporting the viral load in log IU/mL units helps the doctor accurately interpret changes in viral load and better assess a patient's response to treatment.

Question 2. What do these test results mean: “<43 Detected” or “<43 Not Detected”?

According to the reagent manufacturer, the lower limit of detection differs from the limit of quantification. The lowest viral load this assay can accurately quantify is 43 IU/mL, but the limit of detection is 7.1 IU/mL for genotype 1 viruses, and 10 IU/mL for viruses with all other genotypes. Therefore, we can qualitatively report detection even if the viral load is under 43 IU/mL (ie, <43 Detected). Thus, “<43 Detected” means the assay was able to detect HCV RNA but was not able to accurately quantitate the viral load (ie, RNA >7.1 or >10 IU/mL, but <43 IU/mL). A “<43 Not Detected” means the assay did not detect HCV RNA (ie, RNA <7.1 or <10 IU/mL). This is compliant with the package insert guidelines for the new direct-acting antivirals boceprevir and telaprevir.

If a quantitation below 43 IU/mL is desired, please order the Heptimax®HCV RNA test. This test provides our broadest analytical measurement range. By combining real-time PCR and transcription mediated amplification (TMA) technology into a progressive test, we can report a viral load range between 5 and 69,000,000 IU/mL. This is the most sensitive HCV RNA test available.

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
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