The question of RVR

[Tekelcat]

I am confused about what RVR means in quantitative terms about when it is supposed to occur. I'm on a Gilead SOC plus one or two new drugs. In the trial protocols, RVR is as <25 in Week 4 . I was at 33 at Week 4 and didn't go < 25 (UD) until week 6. In the trial, this means I must tx for 48 week, and they've hinted my chances of SVR are reduced. But many research papers I read set RVR at Week 4 <50, which I was. What on earth does it all mean. Help?

[can-do-man]

Weather >25, >43 or >50 it doesn't really matter when it comes to being detected.

Interpretation Provides information to assist in interpretation of the test results
An "Undetected" result indicates that hepatitis C virus (HCV) RNA was not detected in the specimen. A titer result indicates the presence of HCV infection with active viral replication.

A "Detected" result with the comment "HCV RNA level is <43 IU/mL (<1.63 log IU/mL). This assay cannot accurately quantify HCV RNA below this level." indicates that the HCV RNA level is below the lower limit of quantification for this assay. When clinically indicated, follow-up testing by this assay is recommended in 1 to 2 months. For the purposes of assessing response-guided therapy eligibility, an "Undetected" result is required; a "Detected" result below the limit of quantification should not be considered equivalent to an "Undetected" result.

http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/83142

[Tekelcat]

OK, yes, I understand that the goalposts for RVR have shifted thanks to more sensitive assays, but what I don't quite get is how when the earlier assays set RVR at <50, as a GT1a, CC, 10.7 million baseline VL, no cirrhosis and low-mid fibrosis, 60 years of age, my chance of SVR was estimated at more than 80%, but now that the assay sets RVR at <25, my hepa informs me that since I didn't reach this RVR at Week 4, my chance of SVR has been reduced to maybe 60%.

[flcyclist]

If I recall correctly, last year Labcorp improved their standard RT-PCR from <43 to <25 for their lower limit of quantification (LOQ).  This improved sensitivity has allowed the protocols of futility rules to change for making trt decisions.  The publications you are likely reading reference the older PCRs and futility rules.  As far as I know Quest still uses <43 (LOQ) for thier standard RT-PCR, but both Quest (<5) and Labcorp (<2) both have a more sensitive test if desired.  

[OC]

RVR (Rapid virological response)= No virus detected at week 4.
eRVR(Extended rapid virological response) = No virus detected at week 4 and week 12.
EVR (Early Virological Response) = 2 log drop of HCV RNA after 12 weeks.
cEVR = Complete Early Virological Response — No virus detected after 12 Weeks.
SVR12 (Sustained virological response)12 = No virus detected at 12 weeks after completion of treatment.
SVR24 = No virus detected at 24 weeks after completion of treatment

Null response - Failure to reduce HCV RNA by at least 2 logs10 (100 times) after 12 weeks of prior treatment, which is the currently recommended Food and Drug Administration (FDA) definition for clinical trials of investigational hepatitis C treatments.

Partial response - At least a 2-log10 (100-times) drop in HCV RNA, but inability to fully remove the virus from the blood by week 24.

Breakthrough - After dropping to undetectable levels, HCV RNA is detected again in blood during treatment.

Relapse - After dropping to undetectable levels, HCV RNA is detected again in blood after treatment ends.

[desrt]

RVR means undetected at week 4.  Less than 25 or less than 50 are simply the sensitivity of the tests used. If you had used a <50 test, you wouldn't have been truly UND, it would mean you had used a less accurate test.