Introduction
Epidemiological indicators on hepatitis C in France indicate that this disease is a public health issue as regards the number of persons affected (500 000 to 650 000 persons), long term complications, and not yet fully controlled transmission modes, in particular in drug users. Following the identification of the hepatitis C virus in 1989 and the development of diagnosis tests, the rapid progress of viral, biological, clinical and epidemiological knowledge has allowed to implement prevention measures, targeted screening and a more efficient management of patient care.
In 1999, the French health authorities brought together a national programme to control hepatitis C. In order to contribute to the evaluation of this programme, the Institut de Veille Sanitaire (INVS, National public health institute) has developed two national surveillance networks: surveillance of patients newly managed in specific hospitals and surveillance of hepatitic C screening through laboratories (RENA-VHC network) in order to monitor trends and to characterise persons -in terms of age and sex- screened positive for hepatitis C. This article presents the results of the first two years of surveillance of RENA-VHC.

Methods
Definitions
For this surveillance, the following terms were used:
Screening test: search for antivirus antibodies specific to hepatitis C virus (HCV) using ELISA test on a first blood sample.
Validation of screening test: validation of a positive screening result testing a second blood sample using a test or a technique different from the ones used for the screening test. The validation test is either a test for searching anti-HCV antibodies (ELISA or Immunoblot) or a test for viral RNA search (qualitative PCR).
Overall activity: overall number of blood samples taken for screening, validation of screening and for searching anti-HCV antibodies with no indication on the prescription context, over a given period of time (month, quarter or year). The structure of the data collection did not allow to differentiate those three types of samples. ELISA and Immunoblot were the techniques used.
Validation of screening: overall number of blood samples taken for a validation of screening whatever the technique used (ELISA, Immunoblot and PCR), over a given period of time (month, quarter or year).
Overall indicator of positivity: rate of the overall number of anti-HCV antibodies positive tests whatever the prescription motivation was (screening tests, tests to validate screening , un précised indication) over the overall activity.
Validation indicator of positivity: rate of the number of tests to validate screening found positive over the overall activity. A person was defined as confirmed positive for HCV if both tests - screening and validation of screening - were found positive.

Organisation of the surveillance network
The laboratories invited to participate in RENA-VHC were those that took part in the national surveillance network for HIV (RENAVI) in 1997 (1). They were spread all over France except for Corsica region. They could carry out the tests themselves or have them done by other laboratories. They were either hospital laboratories (157 laboratories contacted), or private ones (200 laboratories). Their participation in the network was on a voluntary basis.
All blood samples (except those of children under one year of age) tested for hepatitis C in a participating laboratory were included in the surveillance, whatever the test used (ELISA, Immunoblot, qualitative PCR). When a laboratory did not carry out the tests itself, the results were included in its surveillance activity. Laboratories ended up with two types of activity reports:
- a monthly report including: overall activity, validation of screening activity, overall number of anti-HCV serologies found positive, and the number of validation of screening tests found positive. These data were collected depending on the type of test used (ELISA, Immunoblot, qualitative PCR) and on the persons' gender.
- a monthly report of positive blood samples: for each HCV positive sample (sample for screening and for validation of screening) the indication and the type of test used, the person's gender, age or year of birth were indicated.
These reports were sent to the Institut de Veille Sanitaire on a quarterly basis. The laboratories' participation to RENA-VHC was defined by sending at least one quarter's worth of data to the InVS.

Results
Participation
The 357 contacted laboratories represented 10.4% of all the laboratories carrying out or delegating anti-HCV serologies (n=3420) in France. Among the laboratories contacted, 281 accepted to participate, 17 refused and 59 never answered. Among the 281 laboratories, 260 (93%) took part in RENA-VHC for at least one quarter in 2000-2001. They were split between 132 private laboratories (51%) and 128 hospital laboratories (49%). Among the 260 laboratories, 189 (73% of those that agreed) participated all along the eight surveillance quarters, and 71 participated irregularly over one to seven quarters.

Results from laboratories (n=260) that participated for at least one quarter in RENA-VHC for the period 2000-2001
Those 260 laboratories represented 6.3% of all the laboratories carrying out or delegating anti-HCV serologies. They were spread all over France (Figure 1). Their overall activity represented 947 644 samples carried out to search for anti-HCV antibodies. Their validation of screening concerned 14361 samples. These laboratories reported 27 862 positive samples through the monthly reports. Among them, 61% resulted from screening, 35% from validation of screening , and for 4% the indication of the prescription was not mentioned. Over the two surveillance years, 9637 persons (35%) were confirmed positive for HCV in these laboratories.

Results from laboratories (n=189) that participated continuously in RENA-VHC during the eight quarters of the 2000-2001 period
Geographical distribution
The 189 laboratories were divided into 91 private laboratories (48%) and 98 hospital laboratories (52%) and represented 4,6% of all the laboratories performing or delegating anti-HCV serologies.
Overall activity
In total, 361 832 anti-HCV serologies were tested with an ELISA or Immunoblot in 2000, versus 397 759 in 2001, representing an increase of around 10% (Table 1). For each year, the overall activity concerned a higher proportion of women (45%) than men (43%; p<0.001), with 12% of tests for which no information on gender was available.

Overall indicator of positivity
Among the 361 832 serologies carried out in 2000, 14 814 were found positive for anti-HCV antibodies (ELISA or Immunoblot). The overall indicator of positivity was therefore 4.0 %. In 2001, it was slightly lower : 3.8% (15 256 positive serologies on 397 759, p=0.01) (Figure 2).
The overall indicator of positivity was higher each year for men (5.7% in 2000 and 5.2% in 2001) than for women (3.6% in 2000 and 3.4% in 2001) (p<0.001), but also higher in 2000 than in 2001 in both men (p<0.001) and women (p<0.001).

Validation of screening
In 2000, 5363 samples were tested for validation of screening, and 5165 in 2001. Tests to validate screening represented 1.5% of the overall activity in 2000 and 1.3% in 2001. The proportions of each technique used were 76% in 2000 and 71% in 2001 for the ELISA or Immunoblot tests (n=4089 in 2000, n=3650 in 2001) and 24% in 2000 versus 29% in 2001 for qualitative PCR (n=1274 in 2000, n=1515 in 2001).

Validation indicator of positivity
In 2000, validation indicators of positivity were 1.2% (n=4344 tests to validate screening found positive) versus 1.0% in 2001 (n=3797 tests to validate screening found positive), (p<0.001) (Figure 2). The validation indicator of positivity was significantly higher in men (1.7% in 2000 ; 1.3% in 2001) than in women (1.0% in 2000 ; 0.8% in 2001) for each year (p<0.001) and higher in 2000 compared to 2001 for each gender (p<0.001).
Inter-regional distribution of the validation indicator of positivity in 2000 and 2001 for the 189 laboratories having continuously participated in the surveillance
Laboratories have been gathered into five inter-regions following the telephone code for inter-regions. For each year, the validation indicator of positivity was distributed heterogeneously within the inter-regions. The highest value was observed in the Ile-de-France region. For each inter-region, this indicator declined between 2000 and 2001 (p<0.001)
(Table 2).

Distribution by age and sex of HCV positive confirmed persons over 2000-2001
For the 189 laboratories that participated for eight quarters, the total number of positive samples recorded in the monthly reports was 21 989. Among those, 7588 (35%) were found positive for the validation test and represented 7588 HCV positive confirmed persons: 4557 were men, 2972 women (sex-ratio men/women = 1.5 for each year) and 59 were of unknown gender (anonymous screening). Age characteristics were similar for both years: the mean age was 48 years (median 43 years) and ranges from 1 to 97 years. The age was not documented for 93 persons (anonymous screening and missing data).
Over the two years, the proportion of men confirmed HCV positive was more important in the age groups 20-49 years compared to women in the same age groups, and peaked at 31% in the age group 30-39. In groups aged 50 and over, women confirmed positive were predominant, with in particular 17% of women in the age group 70-79. However, in the whole population, the majority of women confirmed positive (22%) was in the 30-39 age group, just like for men (Figure 3).

Discussion - Conclusion
The laboratories' committment during these first years of surveillance of HCV screening activity was very good over the period 2000-2001 considering that 260 of the 281 (93%) laboratories that were willing to participate have sent quarterly results at least once. Among those 260 laboratories, 71 had a disrupted participation that can be explained by: a temporary disruption of data collection (n=41), a start after the 1st quarter 2000 (n=11), a definitive (n=15) or non documented (n=4) disruption. Some reasons given were the complexity of data collection, the difficulty in accessing computer tools that can easily extract the RENA-VHC data out of all the laboratory data, or an important workload.
For 189 laboratories that participated on a regular basis, the yearly overall activity slightly increased from 2000 to 2001 with some fluctuations in the course of the quarters. The validation of screening decreased slightly during the same period. The stable overall activity observed during the 1st quarter 2000 could reflect either the basic activity of RENA-VHC or the setting-up of surveillance. The activity diminishes during the summer quarter, then increases between the 4th quarter 2000 and the 2nd quarter 2001. This could be linked to the promotion of information and incitement towards screening by the Ministry of Health for the attention of health professionals in June and July, then in October 2000. The decrease observed later corresponds to the summer season. The 4th quarter increase could be linked to the impact of campaigns intended to the general public (broadcast campaigns on radios in May, then in October-November 2001, as well as national and regional daily newspapers campaigns in June 2001).

The overall indicator of positivity tends to diminish slightly between 2000 and 2001 (4.0% in 2000 and 3.8% in 2001). These proportions of positive samples are similar to the results found in 1997 in a survey on HCV screening in community practices in the Doubs and Ile de France regions (2), which revealed a proportion of 5.1% anti-HCV positive serologies. All these results concerned serologies carried out for both screening and validation of screening . This can explain that those proportions are higher than those reported in prevalence studies (3,4).

The proportion of all the positive samples was more important in men (5.5%) than in women (3.5%). This disparity was also found in the study on the Ile de France and the Doubs regions (2), with respectively 5.7% in men and 4.5% in women, as well as in another study performed in 1988 on the free HCV screening programme (5.3% in men and 2.2 % in women, for a non-incarcerated population) (5).
The validation indicator of positivity was significantly lower in 2001 (1,0%) than in 2000 (1.2%), and can be explained by the increase of the overall activity, but remained comparable to the 1.2% of HCV confirmed diagnosis in the prevalence study on persons benefiting from social security (3).
Each year, variations of the validation indicator of positivity were observed between inter-regions. For each one of them, the indicator declined from 2000 to 2001 but remained comparable to the regional seroprevalence data on HCV in 1994 (3). For instance, the prevalence in the Lorraine region was 1.1% in 1994 (3) and the validation indicator of positivity of the region 3 was 1.2% in 2000 and 0.9% in 2001. The indicator is the highest in the Ile-de-France region (1.7% in 2000 and 1.5% in 2001) and can be explained by a more important proportion of intravenous drug users (IDU), for whom the prevalence of HCV infection is the highest (5). The indicator of positivity was calculated for the PACA region (Provences-Alpes-Côtes d'Azur) where the population of IDU is high, and its value was also high in 2000 (1.6%) then declines in 2001 (1.2%). The decreases of those indicators can be explained by the increase of the overall screening together with the decrease of tests to validate screening that were found positive. In other words, the screening activity increases but covers more people with little risk of acquiring the HVC infection.

Among the 7588 persons confirmed HCV positive, the age distribution between men and women was very different. The distribution curve peaked in those aged 30-39 for men (31% of men), then regularly declined for the oldest age groups. In women, a same peak was observed for those aged 30-39 years (22% of women), declined in those aged 60-69 years, then a second peak was observed for those aged 70-79 (17%). The high proportion of persons confirmed positive observed in those aged 30-49 years (54% for men ; 39% in women) can be explained by an important proportion of IDUs, either former or current IDUs (5). The high proportion of women confirmed positive between 60 and over 80 (37%) could be due to nosocomial infections and a history of blood transfusions before 1990 (6).
The first two years of surveillance of the RENA-VHC network by laboratories that contributed on a regular basis provided results on the HCV screening in France that are comparable to previous studies, despite two points: the fact that RENA-VHC relies on a small number of volunteer laboratories (4.6% of all the laboratories), and the fact that the regions are unevenly represented (southern regions being less represented). Although the data collection is not old enough to highlight clear trends, or to assert the impact of the screening promoting campaigns organised by the ministry of health, it appears that the screening activity of the laboratories that continuously participated in surveillance increased in 2001 of around 10% compared to 2000. It will be useful to complete these first results with precisions on the population covered by the participating laboratories in order to supply refined national and regional evaluations.

Article reprinted from Bulletin Epidémiologique Hebdomadaire 2003; (16-17): 85-9.

The RENA-VHC laboratories are listed at :
www.invs.sante.fr/beh/2003/16_17/beh_16_17_2003.pdf