Previous studies have defined severe acute hepatitis by an ALT level >5-10 times the upper limit of the normal range.7
This term is important because patients with severe acute hepatitis should be carefully evaluated to identify whether the cause is treatable and to determine whether the clinical course will proceed to acute liver failure.
In this study, 30.9% of 136 patients with severe acute hepatitis were confirmed as having HAV infection on the basis of serologic testing. Patients in the HAV group were significantly younger and had higher initial and peak ALT levels than those in the non-HAV group. These results are relevant to the trend of increasing incidence of AHA in Korean adults. Kim et al reported that the age-specific seroprevalence of protective IgG anti-HAV dramatically decreased among all age groups from 1982 to 2006. Consequently, several outbreaks of HAV have occurred in Korean young adults during the past two decades.3
In countries (such as Korea) where sanitation conditions have recently improved with increased socioeconomic development, it is necessary to ascertain whether HAV is the cause of severe acute hepatitis.
Initial negative IgM anti-HAV in acute onset of AHA means that this is the early stage of clinical course. The study by Hyun et al10
showed the interval from peak-ALT day to the first HAV-test day was associated with the initial result of IgM anti-HAV. The patients with negative initial IgM anti-HAV showed the negative value of the interval from peak ALT to the first HAV test (mean±SD, -1.5±1.5 days).10 This trend also was shown in our data (mean±SD, -1.3±1.3 days), and this suggests that IgM anti-HAV has limitation to early diagnosis of AHA during window period.
In this study, the detection of HAV RNA through RT-PCR was concordant with detection of IgM anti-HAV, with a good kappa value (0.707). When an equivocal result of anti-HAV IgM was regarded as negative, the sensitivity and specificity of HAV RNA were similarly high between the serologic test and HAV RNA detection by RT-PCR. Therefore, the molecular approach of HAV RNA detection was comparable to the serologic test of anti-HAV IgM HAV.
When we analysed the discordant sample cases between the two tests, all eight patients with negative or equivocal anti-HAV IgM and positive HAV RNA results were confirmed as having AHA by subsequent serologic tests. Because HAV is a major etiologic cause of severe acute hepatitis, IgM anti-HAV is usually included in first-line laboratory examinations in such cases. However, serologic tests with IgM anti-HAV may provide a false-negative result during the window period.
In a study of 195 children with IgM anti-HAV negative results during an HAV outbreak in a public school and a child care center, de Paula et al reported that a considerably high (12-13%) proportion showed positive HAV RNA results.4
Among 143 patients confirmed as having acute hepatitis on the basis of IgM anti-HAV by commercially available solid-phase radioimmunoassays during an outbreak, Liaw et al demonstrated that six patients (4.2%) were initially negative when tested within three days after onset of symptoms.5
Bower et al found that HAV RNA was detected an average of 14.4 days before IgM antibody in experimentally infected chimpanzees, with similar data in humans.6
These findings show that serum HAV RNA is generally detected before IgM anti-HAV, and they suggest that HAV RNA RT-PCR may be more sensitive during the early phase of HAV infection, especially during the window period before antibody to HAV is detected.
Bower et al reported that the duration of HAV viremia was 95 days (range, 36-391 days), and viremia persisted for an average 79 days (range, 18-383 days) after the liver enzyme peak.6
Normann et al reported a case in which 4×104
HAV genome equivalents per mL were detected up to 490 days after the onset of jaundice.11
By contrast, in our study, six cases of confirmed AHA among seven cases with negative HAV RNA and positive IgM anti-HAV results showed negative HAV RNA results within 6-16 days after clinical onset. Most of these patients (4 of 6) were categorised in the recovery phase of the disease. This discrepancy between the present study and others may be due to inaccuracies of the reported time of clinical onset of symptoms. Moreover, the cut-off level of qualitative HAV RNA RT-PCR in this study may be relatively high. Also, this finding suggests that HAV RNA RT-PCR may be less sensitive than IgM anti-HAV after the overt phase of the disease. demonstrates the trend of high sensitivity of HAV RNA RT-PCR in the early phase and low sensitivity in the late phase among confirmed AHA patients. And, this result suggests that HAV RNA RT-PCR is probably more useful in early diagnosis of AHA at least in the patients of whom the duration from clinical onset to admission is within 7 days.
This commercially available multiplex PCR method uses the standardized kit, and performs the automated procedure from nucleic acid extraction to RT-PCR process, can monitor real-time results compared to conventional PCR method using agalose gel to see the results. Therefore, this multiplex PCR method is likely to produce the more rapid and reliable results than conventional PCR method. Also, originally it is developed in order to detect the nucleic acid of HAV, HBV, and HCV simultaneously. Thus, it is capable to diagnose the acute viral hepatitis in window and overt period earlier than serologic test. And it also has advantage in the early accurate diagnosis of overt viral hepatitis in immunosuppressant patients who may not produce the serologic markers.
In summary, 30.9% of 136 patients with severe acute hepatitis were confirmed as having HAV infection, and the concordance between IgM anti-HAV and HAV PCR was 88.2%. The sensitivity and specificity of HAV RNA PCR were equivalent to those of IgM anti-HAV for the diagnosis of AHA. Some cases (19%) of AHA were diagnosed by HAV PCR before the appearance of IgM anti-HAV. In the recovery or relapse phase of AHA, some cases showed negative HAV RNA results. We conclude that the qualitative HAV RNA PCR test has equivalent diagnostic accuracy for the diagnosis of AHA as compared with IgM anti-HAV, and may be more sensitive during the window period.