Acute HCV may present as acute hepatitis like illness with raised bilirubin and liver enzymes but more often has subclinical presentation. Serum Anti HCV is positive after 6-8 weeks and HGV RNA after 2 weeks so serial testing at monthly interval will lead to negative results in about 3 months time. But if the tests are positive even after 6 months then chronic infection is likely.

Much more often chronic HCV is detected on testing for other reaseons like voluntary blood donor or preplacement screen, during routine health check ups or after presentation with other features of chronic liver disease like asymtomatic elevation of liver enzymes or ascites, GI bleed etc. The whole clinical scenario has to be taken into consideration. 

Thank you Gautam for your comments, but what you have mentioned is well-known. It has been shown in a one study  that there is  specific immunoassay testing help to distinguish acute from chronic HCV infection,below is the link to that study 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3020409/

please see the most updated CDC case definition of acute HCV on the following link:

http://wwwn.cdc.gov/NNDSS/script/casedef.aspx?CondYrID=723&DatePub=1/1/2012

Thanks for the interesting reference.  Even though this new assay can help differentiating, I don't see a clear benefit from it unless you plan to give treatment for acute hepatitis C.  IFN is toxic for most patients and new medicines are just too expensive.  In the absence of a well documented inoculum (that may justify IFN) these patients can safely wait for possible spontaneous viral clearance which can save potential side effects from medicines and significant expense.

Personally I feel recently elastography has evolved in a great way for making diagnosis of fibrosis , cirrhosis or advanced disease. Fibroscan can be now routinely recommended bedside non invasive procedure for making clinical decision (even without liver biopsy). So fibroscan value of > 5 Kpas goes in favor of chronic HCV (F1 fibrosis). As far as acute HCV is concerned 12 week period is the cut off for spontaneous clearance of virus and any period beyond it should be treated.

You can help With western blot test. 

Old-fashioned liver biopsy still helpful, not only to estimate fibrosis or cirrhosis (these are not the same), but type and degree of subacute and chronic inflammatory processes.

The search for acute HCv among the public may promote panic, but for medical personnel who are subjected to a risky behavior during an accident, monthly check of transferases and HCV RNA for 3-4 times might exclude getting HCV infection form the risky behavior. The aim is certainly to get treatment for 3 months which gives SVR of 3 times higher than spontaneous viral clearance

The current gold standard to diagnose acute hepatitis C is the demonstration of Ab seroconversion in the context of positive HCV RNA and elevated liver enzymes. I concede that it is sometimes difficult to show what is usually found in the early phase only but this is the one and only way to diagnose acute HCV.

Acute HCV infection can be demonstrated only when it is present an antibody seroconversion in the presence of HCRNA positivity. No more. Amitawa said that fibroscan could be useful to differentiate acute from chronic phase. I believe that Fibroscan is not absolutely useful to  differentiate acute from chronic hepatitis C. During the acute phase fibroscan value can show a high value expressed as KPa but this could have been due to high inflammatory state of the liver and not expression of liver fibrosis.

A definite diagnosis of acute HCV infection is still based on the presence of HCV RNA in serum with documented anti-HCV antibody seroconversion. Other criteria that can aid in diagnosing HCV infection include significantly elevated ALT levels (>10 times the upper normal limit), known or suspected exposure to HCV within the preceding 6 months and increasing numbers of reactive proteins in a recombinant immunoblot assay.

Take a good history

Find out if there are any previous lab samples which could be tested

Ask virology to perform an avidity assay which can help to distinguish acute and chronic infection

Pre-infection testing is key for confirming seroconversion. Avidity assays have not been validated for HCV, and there are no accepted breakpoints, so they will not be readily interpreted/accepted as evidence.

Symptomatic acute hepatitis C is usually characterized by a dramatic increase of transaminases and bilirubin, the patient has all symptoms related to classic acute hepatitis. In this case , depending from the period of incubation,  anti-HCV may be undetectable or detectable and HCV-RNA positive. So it is easy to conclude, irrespective of seroconversion status , that this is an acute hepatitis C.

The other cases of acute hepatitis C with no dramatic increase of transaminases usually are not diagnosed, and represent the majority of cases. Probably, demonstrate seroconversion is more important in those cases in which the transmission is suspected