What are the current ways of checking a positive result in an Hepatitis C screening test ?
		Is it necessary to order a quantitative blood HCV RNA test as soon as a case of hepatitis C has been diagnosed ?
		On what basis would you make the choice between a standard method (with a threshold sensitivity of 400 copies/ml) and an ultrasensitive method (which can detect 50 copies/ml) to measure viral load (HIV1 RNA) in plasma (PCR monitor Roche) ?

What are the current ways of checking a positive result in an Hepatitis C screening test ?

The current consensus is that a positive HCV serological screen result should be followed up with a second test based on a different technique and using a new serum sample.
The second method may be a membrane test (e.g. a RIBA test) but using a second kind of ELISA-which is different from the first but gives the same information-should be preferred because modern ELISA tests are more sensitive than membrane tests. If both ELISA tests give a positive result, it can be concluded that the patient is seropositive. If the two tests give opposite results, the patient's serological status remains uncertain and how to proceed with the diagnostic procedure will be determined by the clinical picture and the results of other tests, including liver function, serological re-testing at a later date, and a PCR HCV RNA test.
If you are going to send us a sample for follow-up HCV serological testing, please indicate the ELISA method already used and, if possible, the result obtained. This is so we can be sure to use a different technique.
 

Is it necessary to order a quantitative blood HCV RNA test as soon as a case of hepatitis C has been diagnosed ? y

No
The initial investigation should focus on determining whether or not the virus is multiplying using a qualitative PCR assay. The viral load as measured by the amount of HCV RNA in the blood does not reveal the severity of the infection which can only be reliably estimated by histological analysis of a liver biopsy. Quantitating HCV RNA is only of use when it comes to trying to decide on a therapeutic strategy; in this situation, the viral genotype should also be determined in order to help with the selection of the most appropriate treatment modalities.

On what basis would you make the choice between a standard method (with a threshold sensitivity of 400 copies/ml) and an ultrasensitive method (which can detect 50 copies/ml) to measure viral load (HIV1 RNA) in plasma (PCR monitor Roche) ?

The two different methods do not have the same accurate ranges. Standard techniques are linear between 400 and 750,000 copies/ml whereas the ultrasensitive technique is only linear between 50 and 75,000 copies/ml. We use the ultrasensitive method from the outset for all patients for whom the order is explicit (patients known to have a low viral load) and for any patient who we know to have given low results in the past. On the other hand, for all "new" patients and patients with a history of high results in the past, we use the standard method first.
It is extremely important that the patient's full name and date of birth be accurate and legible on the Test Order Form: this is so we can take previous test results into account.