Hepatitis C virus carriers with persistently normal aminotransferase levels: healthy people or true patients?

CLINICAL REVIEW

OlGESTLlUER DIS 2001J;32:634-43

Hepatitis C virus carriers with persistently normal aminotransferase levels: healthy people or true patients? C. Puoti R. Castellacci F. Montagnese

Dept. of Internal Medicine and HepetoG8Stmnt@~Ology,

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I Dr. C. Puoti, via Cimone 171. 0014 I

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Since the discovery of hepatitis C virus, the availability of serological hepatitis C virus screening has led to the identification of many subjects with normal aminotransferase levels who are chronically infected by the hepatitis C virus. To date, the epidemiology and natural history of subjects with normal aminotransferase levels are far from being clarified. Further: whether subjects with persistently normal aminotransferase levels should routinely undergo liver biopsy is still extremely controversial, and benefit from interferon treatment in this group of patients is yet to be proven. On account of the consistent normality of aminotransferases, it is not easy to calculate the rate of persons with normal aminotransferase levels among chronic hepatitis C virus carriers, nor their prevalence in the general population. It has been estimated that up to 25% of patients with chronic hepatitis C virus infection have persistently normal aminotransferase levels (10% to 40% according to different studies]. Most studies showed a clear prevalence of females, ranging from 58% to 90%. Liver biopsy shows some degree of chronic liver disease in up to 80% of these subjects, although in the majoriv, histological damage is mild and probably does not progress to more severe liver disease, moreover: the progression to fibrosis is slower than in patients with elevated aminotransferase levels. Virological features of these subjects [hepatitis C virus genotype distribution, viral load, quasispecies diversity] do not differ with respect to patients with elevated aminotransferase levels although a higher frequency of non 1 hepatitis C virus types has been reported. To date, no biochemical or virological tools to assess the presence and severity of liver damage exist. Antiviral treatment with interferon may induce a long-term response in only a small proportion of hepatitis C virus carriers with persistently normal aminotransferase levels, and many patients develop aminotransferaseflare-up during or shortly after treatment. Thus, interferon or combination antiviral treatment of hepatitis C virus carriers with normal aminotransferase values should be avoided in clinical practice.

Digest Liver Ok 2000;32:634-43 Key

words: aminotransferase;

HCV; histology:

interferon

E-mail: hbffa@%n.it

Since the discovery of hepatitis C virus (HCV), the availability and widespread use of serological HCV screening has led to the identification of many subjects with normal aminotransferase (ALT) levels who are chroni-

C. Puoti, et al.

tally infected by the HCV I-3 and, indeed, it has now become clear that many subjects with chronic HCV infection show persistently normal aminotransferase levels (PNAL). Although formerly referred to as “healthy” or “asymptomatic” HCV carriers ‘, evidence is growing that many of these patients present histological liver damage, sometimes severe, despite their persistently normal liver biochemistry 4-‘4. Thus, the terms “healthy” or “asymptomatic” are inappropriate. In clinical practice, the optimal management of HCV carriers with PNAL remains to be established, and many questions remain unanswered. For example, the epidemiology and natural history of subjects with PNAL are far from being clarified; conflicting data exist as to whether these patients have milder histological lesions than those with abnormal ALT levels 4, and it has not been fully established whether virological features differ significantly between subjects with normal and those with abnormal aminotransferase levels; finally, whether subjects with PNAL should routinely undergo liver biopsy is still highly controversial, and the benefit of IFN treatment in this group of patients is yet to be proven.

Definition A widely accepted definition for this subset of patients takes into account: 1. presence of antibodies to HCV (anti-HCV); 2. positivity of HCV RNA by polymerase chain reaction (PCR), and 3. persistent normality of ALT levels 15. It should be stressed that anti-HCV positive/RIBA confirmed patients with negative HCV RNA should be retested for PCR on at least three different occasions, 3-4 months apart, in order to rule out the possibility of intermittent viraemia or of false-negative results, and to identify subjects with resolved HCV infection 16-‘*. ALT should then be retested on at least three different occasions, two months apart over a 6-month period. In fact, many studies have shown that 30% to 50% of HCV carriers with normal ALT levels, on one occasion, may have ALT flare-ups during a 6 to 12 months’ observation period I9 *O.Thus, although standard definitions Is I’ suggest a 6-month follow-up period, it seems reasonable that HCV carriers with PNAL should be retested for ALT every three months over a period of at least one year.

HCV carriers, nor their prevalence in the general population. Indeed, these subjects are usually discovered by chance, in coincidence with blood donations, screening of relatives of anti-HCV positive patients, screening in high-risk groups, routine checks, pregnancy, endoscopy, surgical or dental care, etc. It has been estimated I5 *’ that up to 25% of patients with chronic HCV infection have persistently normal ALT levels (10% to 40%, according to different studies) lo I2 *O22-24.It is worthwhile mentioning three important studies 25-27,which greatly contributed to clarifying the prevalence of anti-HCV positive subjects with PNAL in the general population (Table I). However, due to the lack of HCV RNA determination in two of these studies 252h, the true prevalence of HCV carriers with PNAL remains to be evaluated. The Dyonisos study 25, a prospective cohort study aimed at investigating the prevalence of chronic liver disease (CLD) in the general population of two small towns in Northern Italy, reported a prevalence of anti-HCV positive subjects with normal ALT levels of 1.5%. In a similar study performed in the general population of a small town in central Italy, Stroffolini et al. *’ found that the overall prevalence of anti-HCV positive subjects with PNAL was 2.5%. Finally, in a third study *‘, the prevalence of HCV infection was assessed in the general population of a town in Southern Italy. The overall prevalence of anti-HCV positive, RIBA confirmed subjects with PNAL was 12.0% HCV RNA was detected by PCR in 84.7% of RIBA-confirmed subjects. As HCV RNA was detected by PCR in 84.7% of RIBA-confirmed subjects, one could infer that the prevalence of HCV carriers with PNAL in Southern Italy is 10%.

Table I. Prevalence of anti-HCV positive carriers with PNAL in different population samples. Authora hf.1 McLindon et al. I1 Ryan et al. 2 Bellentani et al. 25 Stroffolini et al. 26 Puoti et al. 24 Guadagnino et al. 27 PNAL: persistently

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Sam& Blood donors Blood donors General population General population In-patients General population

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0.02% 0.07% 1.5% 2.5% 4.7% 12.0%

levels

Demographicfeatures Epidemiology Given the consistent normality ofALT, it is not easy to calculate the rate of persons with PNAL among chronic

As far as concerns demographic features of subjects with PNAL, most studies 4 9 28 29 showed a clear prevalence of females, ranging from 58% to 90%, the ma-

635

jority of patients with abnormal ALT being males 4. Only two studies performed in blood donors ” 3ofound a prevalence of males. Alcohol consumption was higher in patients with abnormal ALT in one study 9, while other studies did not find significant differences in alcohol intake between subjects with normal or abnormal ALT levels 4 12.Mean age was found not to differ in some studies 4 9 l4 31 whilst according to other authors, carriers with PNAL were older I2 or younger ** than subjects with abnormal ALT levels. Another important issue concerns the frequency of epidemiological risk factors in carriers with PNAL. Data from the literature are conflicting. We found 4 a low frequency of history of exposure to blood in subjects with PNAL as compared to patients with abnormal ALT (37% vs 65%, p
The time of appearance of ALT abnormalities ranged from 1 to 26 months after the start of the study. Overall, these findings suggest that at least two sub-groups of subjects with PNAL exist: patients with wide temporal ALT fluctuations that could be within the normal range for several months, and subjects who show persistently normal ALT levels. A study aimed at evaluating the progression of histological damage in 37 subjects with PNAL found that liver biopsy performed after five years of follow-up was no different from that performed at the enrolment in the study 35. Liver biopsy revealed histological features of mild to severe chronic active hepatitis in 34 patients, and normal liver in three patients 35. At the end of the study, 73% of the patients still had normal ALT levels. This finding further suggests that the course of HCV infection in subjects with consistently normal ALT levels seems to be very slow I5 35. Do HCV carriers with PNAL spread HCV infection? Although this is an important issue in clinical practice for the counselling of the patients, there are few studies addressing this point in small series of patients. In the study of Ryan and co-workers, only l/27 (3.3%) of sexual partners of HCV carriers with PNAL was found to be infected 2. In this study, no data regarding relatives of patients with abnormal ALT were given. Another study found no anti-HCV positivity in relatives of subjects with PNAL, vs 15% of anti-HCV positivity detected in partners of patients with raised ALT 37. In these two studies, however, no data regarding HCV RNA were given, thus this finding could be, at least in part, explained by the absence of HCV RNA in some anti-HCV positive patients with PNAL. In a study aimed at comparing the prevalence of anti-HCV in relatives of HCV carriers with normal and abnormal ALT levels 38, we evaluated 50 relatives (30 spouses and 20 children) of 34 HCV RNA positive carriers with PNAL and 212 relatives (162 spouses and 50 children) of 180 patients with raised ALT. We found no anti-HCV positive persons in the families of subjects with PNAL, vs 11.7% of spouses and 2% of children of subjects with abnormal ALT. This unexpected finding, however, should be cautiously interpreted, as the small numbers of patients studied, the lack of HCV RNA determination in two out of three studies * 37and the lack of HCV RNA quantification and of HCV genotype determination in the third 38 greatly reduce the clinical relevance of this observation.

Liver histology Two main questions should be answered. First, do HCV carriers with PNAL have significant liver dam-

age? Second, do these patients have milder liver disease than those with abnormal ALT? Although early studies 39 suggested the possibility of the existence of HCV carriers with normal liver, evidence is growing that HCV carriers with PNAL have significant liver damage despite consistently normal liver biochemistry. However, to date, remarkable controversies exist as to whether these patients have milder histological lesions than those with increased aminotransferase levels 6. A recent review showed that less than 30% of patients had normal liver 40; when more recent studies were evaluated, this figure decreases to less than 20% (Table II). 4% of cases had minimal chronic hepatitis (CH), 52% had mild CH, 23% had moderate to severe CH, and 1.3% had cirrhosis (Table II). Pagliaro et al. 41 analysed 19 published studies comprising a total of 764 HCV positive carriers with PNAL (HCV RNA positive in 14 studies, RIBA positive in 4, anti-HCV positive by enzyme-linked immunosorbent assay (ELISA) in 1). The prevalence of severe CAH in these patients was nil in 7/12 studies, ranging from 2% to 7% in the remainder. By contrast, the median prevalence of severe CAH in patients with abnormal ALT values was 24%. However, it should be noted that in 5 out of the 19 studies evaluated by Pagliaro et al., patients were not tested for HCV RNA, and thus also HCV RNA negative subjects - who show normal liver 5 ’ - could have been included in this evaluation. One study comparing liver histology in subjects with PNAL and with raised ALT levels found that necroinflammatory grade, stage of fibrosis and estimated rate of fibrosis progression were significantly lower in patients with PNAL 42. This important study confirmed that activity and fibrosis scores in subjects with PNAL were significantly lower than those of patients with abnormal ALT levels even after exclusion of HCV RNA negative subjects or of heavy drinkers, whereas virological features were similar. Only 6% of normal ALT patients, as compared with 20% of elevated ALT patients, showed a fibrosis score higher than 2. Furthermore, the authors found that severe fibrosis was associated with alcohol consumption in patients with normal ALT 42.

Wla II. Liver histology in I-KS carriers with PNAL. 15 published studies Normal liver Minimel chronic hqvsitis Mild ~hmnio hwtitie ModereWsevere chronic hapetitis Liver cirrhoeis

I 392 ceses 19.7% 4% 52% 23% 1.3%

IRefs: 4, 7, 9, IQ, Ii?, 14, 29, 30. 39, 36 43, 55, 67, 71, 741

By contrast, our data show that liver damage is not milder in subjects with PNAL than in those with abnormal ALT levels 4. Moreover, it is noteworthy that 26% of subjects with PNAL and only 6% of those with raised ALT had moderate to severe hepatitis (~~0.02); cirrhosis was found in 1 patient with PNAL but in none of those patients with raised ALT 4. Other authors found severe liver damage in patients with PNAL ’ lo 14. Why, in these studies, subjects with PNAL showed a trend toward more severe liver damage is not clear. We suggested that the lack of any abnormality in ALT levels could result in a long delay in the identification of such patients, unless anti-HCV determination is incidentally performed 4. By contrast, it is possible that, in patients with abnormal ALT, liver biopsy is performed earlier than in those with PNAL, because the finding of abnormal liver biochemistry allows prompt diagnosis of CLD 4. Further, sampling errors on biopsies should be taken into account. Stanley et al. l4 found that 20% of subjects with normal ALT levels had cirrhosis, and 67% had significant fibrosis. Of the patients with raised ALT, 16% had cirrhosis and 62% had fibrosis. The association of normal ALT with cirrhosis was reported by others 4 ’ l2 l9 *O. In conclusion, although the milder histological changes detected in the majority of subjects with PNAL could predict a more favourable outcome than that in patients with abnormal ALT levels, the possibility of severe liver damage despite normal ALT could not be ruled out. This finding highlights the danger of any false sense of security given by persistently normal ALT levels in subjects with chronic HCV infection. Why do many HCV carriers show persistent ALT normality? It is generally assumed that ALT are reflectors of liver disease activity 43, although no strict correlation exists between serum ALT values and the severity of liver cell necrosis and of inflammatory response +‘. In clinical practice, ALT measurement is widely used as a marker of the presence or severity of liver disease. To date, at least two important issues should be answered: first, whether HCV carriers with PNAL could have a weaker immune response to HCV-infected liver cells than patients with raised ALT, and, secondly, why some people have persistently normal liver enzyme levels despite severe histological activity, and vice versa. As to the first point, some studies have considered the possibility of infection with low virulent HCV strains 3645, or of faulty immune reactions to infected liver cells 46. The hypothesis that HCV carriers with PNAL may have some degree of immuno-tolerance seems to be supported by the mild inflammatory infiltrates found in the liver of many subjects with PNAL 46, and by the finding of ALT flare-ups in most IFN-treated patients 637

HCU carriers

with normal ALT

with chronic hepatitis C and normal ALT. These ALT elevations during or shortly after IFN withdrawal may be, at least in part, due to the enhanced immune response induced by IFN, or to an enhanced expression of histocompatibility antigens on the surface of liver cells. Kuzushita et al. 47 found an increased frequency of human leukocyte antigen (HLA) DR13 in HCV carriers with normal ALT levels with respect to patients with elevated ALT levels (42% vs 4%), while the frequencies of HLA class I antigens and intercellular adhesion molecules 1 (ICAM) on the hepatocyte membrane were significantly lower in “asymptomatic” patients than in those with abnormal ALT 47. These lindings suggest that the cellular immune response in HCV carriers with PNAL is less activated than in patients with elevated ALT, and that HLA DR13 could be associated with both low biochemical and histological activity in these subjects. As far as concerns the second issue, it is not easy to explain the reasons why many HCV carriers with histological features of severe chronic hepatitis show PNAL in spite of the severity of liver damage. Data in the literature are few and conflicting, and no studies have specifically addressed this puzzling issue. In general, ALT levels are released by direct virus-related cytopathic activity and/or by immune-mediated processes; subsequently, ALTs are degraded and excreted 48. Zeuzem et al. 48 proposed that these two rate constants (release vs degradation) contribute to the measurable serum ALT levels. The authors suggested that in patients with severe activity and normal ALT levels the rate constant for degradation could be increased, and, conversely, it could be decreased in patients with elevated ALT levels and mild inflammatory liver activity 48. This hypothesis, however, needs further confirmation. Another possibility is that subjects with PNAL could have a higher rate of apoptosis than patients with abnormal ALT. Apoptosis is a physiological mechanism of cell death; it is a crucial event in cell turnover. Histopathological features indicating apoptosis, such as the presence of apoptotic bodies and piecemeal necrosis, are frequently observed in chronic HCV-related hepatitis 49. During apoptosis, but not necrosis, organelle and plasma membrane integrity is preserved, and there is no release of intracellular contents, as cells die by chopping themselves into membrane-packaged bits. A high rate of apoptosis, therefore, could explain the phenomenon of liver cell death in the absence of serum ALT increase. However, early studies did not confirm this interesting hypothesis. Kronenberger et al. 5o studied apoptosis and cell proliferation in vitro and in vivo by TUNEL assay and ant-Ki 67 in a group of HCV carriers with persistently normal or abnormal ALT levels. The authors found that in liver specimens, the rate of apoptosis was very low, and did not differ between the two groups. 638

Virological features Studies addressing HCV genotype distribution, serum HCV RNA titres and quasispecies diversity in HCV carriers with PNAL showed conflicting results. As to HCV genotype distribution, we 4 and others 31 found that HCV type 2a was more frequent in subjects with PNAL, and genotype lb in those with abnormal ALT levels. In other studies genotypes 1 and 2 were observed with equal frequency 30. Shindo et al. 28 found that type 1b was more frequent than 2a both in subjects with normal or abnormal ALT, while Shakil et al. I2 reported that genotype lb was more frequent in HCV carriers with PNAL than in patients with raised ALT. The discrepancies between studies could be due to different enrolment criteria (blood donors vs nonselected patients), to geographic differences or to the different proportion of drug addicts 4. The relationship between HCV genotypes and histological severity in subjects with PNAL is still under debate. Many authors 4 3o 51 52 found no association between HCV genotypes and the degree of liver damage in subjects with PNAL, arguing against any clinical predictive value of HCV genotype determination in these patients. By contrast, others reported an association of type lb 31 53 or of type 2a 54with more severe liver damage. As far as concerns serum HCV RNA titres, some studies showed lower HCV RNA titres in blood donors with PNAL than in patients with abnormal ALT 29ss56, while others found no differences between the two groups 4 l2 284257. It is now generally accepted that serum HCV RNA levels are not significantly different between subjects with normal or abnormal ALT levels 15. Finally, as to the relationship between HCV RNA titres and genotype distribution, many authors 4 365658 reported no significant association between these virological parameters, whereas others found that serum HCV RNA levels were significantly lower in subjects harbouring genotype 2a than in those with HCV type 1b ‘* 54j9. However, it should be stressed that HCV RNA quantification could be influenced by genotypes in some assays 6o. Thus, the discrepancies could be due to the use of a first-generation test which underestimates the amount of HCV RNA in non-l HCV genotypes. Viral heterogeneity (quasispecies diversity) has been correlated with the severity and progression of HCVrelated liver disease 6162. Shindo et al. 28using the PCRsingle strand conformational polymorphism (PCR-SSCP) of the hypervariable region 1 (HVRl) and the immunoprecipitation analysis, found that subjects with normal ALT had a quasispecies nature of the HCV genome similar to those patients with abnormal enzyme levels, and that the virus circulated in the same form (both in immune complexes and in the free form)

in both groups. These data contrast with other findings suggesting a close relationship between the elevation of serum ALT levels and mutations in the HVR of the HCV genome 6162. However, Brambilla et al. 63 reported that the highest rates of HVRl diversification were found in HCV carriers with normal ALT values, who despite persistent viraemia had non progressive liver disease and persistently normal liver biochemistry. Finally, Hayashi et al. 58 found that the HCV core region was very well conserved in patients with normal liver biochemistry but not in patients with abnormal ALT levels, although no significant differences in nucleotide diversity of the HVRl of the E2 region were found. In conclusion, further studies are needed to evaluate whether or not the HCV carrier state with PNAL correlates with lower degrees of virus quasispecies differences. Do serum HCV RNA titres predict the severity of liver damage in subjects with PNAL? In the presence of normal liver biochemistry, no biochemical means of assessing the presence of CLD in HCV carriers with PNAL exists. It follows that, in this group of patients, it is not possible to discriminate between subjects with normal liver or minimal lesions and those with more severe liver damage, unless liver biopsy is performed. This approach, however, implies that all HCV carriers with PNAL should routinely undergo liver biopsy. In clinical practice, a non-invasive test to identify HCV carriers with significant liver damage could be very useful, as it would identify those individuals in whom biopsy is indicated, avoiding this invasive procedure in subjects with possibly normal liver or minimal injury. Only very few studies have attempted to correlate serum HCV RNA levels and liver histology in subjects with PNAL. Some suggested a relationship between the rate of HCV replication and the degree of liver inflammation 28365556but not of fibrosis s 28365564. More recently, we reported 6sthat, in HCV carriers with normal AI-T, no correlation exists between serum HCV RNA levels and grading, while viraemia did correlate with staging. Grading quantifies the severity of interface hepatitis (piecemeal necrosis: score O-4), confluent necrosis (O-6), focal lytic necrosis (O-4) and portal inflammation (O-4); staging evaluates the degree of architectural changes (fibrosis and cirrhosis: score: O-6) @. However, due to the weak and imprecise correlation, we have to conclude that HCV RNA quantification does not accurately predict the presence, nor the severity, of liver damage, and does not improve, in clinical practice, our ability to identify HCV carriers with more severe liver damage. Thus, routine HCV RNA quantification in subjects with PNAL should not be performed, as it is not a useful indicator in the selection of patients candidates for liver biopsy.

Should subjects with PNAL undergo liver biopsy in clinical practice? The role of liver biopsy in HCV carriers with PNAL is still disputed. In fact, although some of these patients will be found to have a severe degree of liver damage 5 ’ l4 the findings that HCV carriers with PNAL show weaker histological activity and lower fibrosis score than those with abnormal ALT 42, that the progression rate of fibrosis is twice as slow as in patients with elevated ALT levels 4267, and that the benefit of IFN in these persons is yet to be proven I5 21, make it difficult to suggest routine liver biopsy for HCV carriers with PNAL, in clinical practice. Furthermore, liver biopsy implies some important disadvantages, such as the risk of complications, poor patient compliance and costs. On the other hand, as repeatedly normal ALT levels do not exclude significant liver damage, liver biopsy could be useful to reassure subjects with normal liver or minimal disease, to identify those with more severe liver damage, and to plan adequate follow-ups. No agreement regarding this important issue exists in the literature. Some authors ’ 3 4 9 68 suggested that liver biopsy should be routinely offered to all subjects with PNAL, while others ‘* stated that, in clinical practice, liver biopsy in individuals with normal ALT should not be considered standard or recommended, and that these cases should be followed up and monitored, but not investigated. Other authors stated that selecting patients for possible liver biopsy only on the basis of abnormal ALT is likely to eliminate from diagnosis many with active or advanced histological disease 67whilst others raised the doubt of what are we hoping to achieve by liver biopsy in HCV carriers with PNAL and what do we have to offer these patients after biopsy 6869. In conclusion, although liver biopsy remains the only tool to determine the presence and the degree of liver injury in patients with PNAL, it should only be performed in those instances in which histological findings are likely to lead to a change in management of the patient 69. As there is, currently, no rationale to treat subjects with chronic C hepatitis and normal ALT levels (see below) l5 21, in agreement with the NIH and EASL consensus conferences 21 69, we believe that liver biopsy should be offered only in established research protocols, thus avoiding this invasive procedure in clinical practice. Should HCV carriers with PNAL undergo inter$eron treatment? The benefit of IFN treatment in this special group of patients is still to be proven l5 21‘O.The rationale for this treatment consists in that subjects with PNAL seem to have less severe liver damage than those with elevated 639

ALT levels. Thus, as IFN therapy is thought more likely to be successful in subjects with mild to moderate disease than in those with more severe chronic hepatitis, this therapeutic option should be particularly indicated in subjects with PNAL in order to evaluate whether their natural history might be changed. Considering the consistent normality of ALT levels, the response to treatment is defined by the disappearance of serum HCV RNA and by the improvement in liver histology. Many of the results available are not from controlled studies 6871-73(Table III); in two studies, a control group was included 4674. In three studies, patients received 3 MU/tiw for 6 months 46” 727576, in the other studies 5 MU/tiw for 6 months 68, 3 MU/tiw for 12 months 74, and 10 MU x 6 months 73 were used. Overall, an end-of-treatment virological response was observed in 34% of patients, ranging from 6% 46 to 67% 68. A long-term sustained virological response (6 to 12 months after treatment) was observed in 12% of patients, ranging from 0 ‘I to 100% 73. Despite promising results, higher IFN doses 6873 or longer courses of therapy 74 cannot be recommended 15. These conflicting results allowed some authors to claim that subjects with PNAL should not be treated with IFN 4671, while others suggested that IFN therapy can be effective in such cases 68‘l. Pre-treatment serum HCV RNA levels and the degree of sequence variability in the HVRl region (complexity of HCV quasispecies) did not correlate with the outcome of treatment, although IFN decreased sequence diversity in all patients 74. Further, the lack of response to IFN in subjects with PNAL seems not to depend on genotype distribution 46. As to liver histology, Serfaty et al. ‘I found that histological parameters (hepatitis activity index (HAI), fibrosis, portal inflammation, piecemeal necrosis, lobular inflammation) were not significantly different in

seven patients who underwent liver biopsy one year after IFN withdrawal, while Sangiovanni et al. found 46 histology improvement only in 17% of the patients (l/6). However, the small numbers of patients studied and the short follow-up period do not allow any delinite conclusions. Many patients (50% to 75%) showed ALT flare-ups during or shortly after IFN treatment 46 7’-74. These flare-ups are more frequent under IFN treatment than in the absence of treatment and it has been suggested that these ALT elevations may be, at least in part, due to the enhanced immunity against liver cells induced by IFN and/or to enhanced expression of histocompatibility antigens on the surface of liver cells, triggering cell-mediated cytotoxicity 46. In fact, in some IFNtreated patients in whom ALT flared-up, HCV RNA load was higher after the flare-up, when enzyme levels returned to normal, than during it 46. In conclusion: a. IFN treatment may induce an overall sustained virological response in a small proportion of HCV carriers with PNAL; b. given the small series of patients and the short-term follow-up, it is not possible to establish whether improvement in liver histology might be seen after treatment, and c. in a high proportion of patients the flare-up of ALT levels occurs during or shortly after treatment. Thus, in agreement with the NIH Consensus Development Conference “Management of Hepatitis C ” I5 and to the more recent Consensus Statement of the EASL International Consensus Conference on Hepatitis C “, HCV carriers with PNAL should not undergo IFN treatment, but they should be followed-up every 4-6 months or entered into clinical trials. In clinical practice, the use of IFN in this special group of patients should be discouraged, and small, uncontrolled pilot trials are not warranted Is. To date, no experience exists on the effects of combi-

Conclusions At least 25% of patients with chronic HCV infection have persistently normal ALT levels on more occasions. Most of them are viraemic (HCV RNA positive). These subjects are more often females and are more likely to be asymptomatic. Liver biopsy shows some degree of chronic liver disease in up to 80% of these subjects, although in the majority, histological damage is mild and probably does not progress to more severe liver disease, and the progression to fibrosis is slower than in patients with elevated ALT levels. Non-viraemic subjects almost invariably show normal liver. Thus, the natural history and the long-term outcome of HCV carriers with PNAL should be good. Virological features of these subjects (HCV genotype distribution, viral load, quasispecies diversity) do not differ with respect to patients with elevated ALT levels although a higher frequency of non 1 HCV types has been reported. To date, no biochemical or virological tools to assess the presence and the severity of liver damage exist, thus liver biopsy remains the only means to delineate the degree of liver injury. However, international conference statements discourage routine liver biopsy. Antiviral treatment with IFN may induce a long-term response in only a small proportion of HCV carriers with PNAL, and many patients develop ALT flare-up during or shortly after treatment. No adequate data on post-treatment histology exist. Thus, IFN or combination antiviral treatment of HCV carriers with normal ALT values should be avoided in clinical practice.

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