Susceptibility to hepatitis A virus infection among chronic liver disease patients and healthy blood donors in Thailand.

Due to improvements in socio-economic and sanitation conditions, Thailand has undergone a change from hyperendemicity to intermediate endemicity for hepatitis A virus infection, leaving a large part of the adult population without immunity. At the same time, the country is still highly endemic for hepatitis B and especially in the northeast, hepatitis C virus infection both of which when acquired during infancy or early childhood exhibit a strong tendency to turn towards chronic liver disease, although in particular with hepatitis B virus the asymptomatic carrier state is also rather common. As no cross-immunity exists between any of these viruses, double or triple infections do occur, a situation where previously acquired immunity to HAV becomes crucial as double infections have been shown to take a more severe or even fatal course. In the present study, we investigated 820 HBV- and/or HCV-related chronic liver disease (CLD) patients and 195 blood donors, both groups divided by 10-year age intervals, for the prevalence of anti-HAV. The results showed the same age dependence of immunity for all groups tested as can be expected for an area of intermediate endemicity, in that approximately 50% of those between 21 and 30 years of age had acquired anti-HAV. These findings indicate the immune response to HAV infection not to be altered by chronic infection with either HBV or HCV. Hence, vaccination against HAV should be considered, particularly in anti-HAV-negative patients with CLD.

Detection of HIV-1 window period infection in blood donors using borderline anti-HIV results, HIV-1 proviral DNA PCR, and HIV-1 antigen test.

Prevention of transmission of HIV-1 via blood transfusion has been carried out by the National Blood Center by screening donated blood with anti-HIV and HIV antigen tests. To increase the safety measure, detection of proviral DNA by PCR has been proposed; however, it was impractical to test all samples by PCR. From August 1994 to September 1995, there were 296,169 blood donors with 0.32 per cent prevalence of anti-HIV positive. From these donors, 153 samples of which the anti-HIV enzyme immunoassay optical density (OD) between cutoff and 80 per cent of cutoff value (borderline results) were selected for PCR testing. One out of 153 borderline cases showed positive by PCR test for HIV-1 proviral DNA. However, this case was also positive by HIV antigen test. Therefore, most of the samples with borderline anti-HIV results were true negative for HIV infection. On the other hand, there were 8 HIV antigen positive samples which had anti-HIV OD below the borderline value determined in this study. This finding confirmed the necessity of using both the anti-HIV and HIV antigen tests for screening of donated blood.

Epidemiologic characteristics of blood donors with antibody to human immunodeficiency virus: Thailand.

Of 782,190 volunteer blood donors in Bangkok and nearby areas, who were screened for infection with human immunodeficiency type 1 (HIV-1) from January 1988 through December 1992, 3,219 tested positive on both enzyme immuno assay and Western blot assay. The identification variables of the donor were collected. The majority of HIV seropositive blood donors were male. The average age (median) of HIV seropositive was 26-29 years all through 1988-2992. The prevalence of HIV seropositive in male donors was higher than that in females. HIV seropositivity was confirmed in blood donations from first-time male donors in this study during 1988-1992. This rate has increased progressively from 0.87/1,000 in 1988 to 15.95/1,000 in 1992 with much higher rates in repeat donors. The repeat male donors increased from 0.77/1,000 in 1988 to 5.26/1,000 in 1991 and since then showed a decreased rate to 3.93/1,000 in 1992. Female donors were infected with HIV more frequently with the prevalence by sex ratio M:F rising from 27:1 in 1988 to 6.6:1 in 1992. Comparing the seropositive rate between first time and repeat female donors, the results showed an increase in rate from 0.11/1,000 in 1990 to 2.02/1,000 in 1992, but essentially the same rate in report donors. A majority of HIV seropositive blood donors (1990-1992) lived in Bangkok (42-49%) and among those who lived in one eastern province (Samut Prakan), 90-93% lived in the industrial areas. Of those who lived in Chon Buri Province, 73-88% lived in Sattaheep District, which is a naval base.

Transmission of HIV infection by seronegative blood in Thailand.

In Thailand, the prevalence of HIV infection in the general population and in donor blood (DB) has sharply increased since 1987. The HIV seropositive rate in DB was increased from 0.0065 per cent in 1987 to 0.95 per cent in 1993 (150 times in 6 years). Heterosexual transmission is the major route of spreading. Therefore, HIV seronegative blood (SNB) poses significant hazard to the recipients because of the risk of viraemia during the window period of early HIV infection. In Thailand HIV Ab screening in all units of blood was started in 1987 and was compulsory nationwide in early 1989. Donor self exclusion (DSE) has been implemented since 1990. It is not fully effective in the prevention of transfusion associated AIDS (TAA) because of many limiting factors. However, DSE should be promoted to practice in every blood bank particularly those that can not do HIV Ag screening. During 1990-1992, there were 30 reported cases of TAA by SNB. The study of risk figure (HIV Ag positive-neutralization with HIV Ab negative) in DB was 1:3,400 and 1:10,000 in two reports in 1991. Under all these circumstances, the national AIDS committee has documented the policy to do HIV Ag screening in every unit of blood from August 1991 and allocated a 10 million baht budget (year 1992) for Ag testing. Several hospitals and NBC reported the risk figures which varied from 1:3,400 to 1:25,000. A certain amount of blood is processed to 2-4 blood components given to 2-4 patients which will increase the number of TAA by SNB.(ABSTRACT TRUNCATED AT 250 WORDS)

Trend study on HBsAg prevalence in Thai voluntary blood donors.

In 1973, the prevalence of HBsAg positive individuals was 9.33% in new army recruit blood donors and 8.28% in the general population (CIEP). The hepatitis B vaccine, which was introduced to use in Thailand in 1985, seems to be effective in reducing the prevalence of hepatitis B carriers year after year. In 1991, the prevalence of HBsAg in new blood donors (74,530) was 6.45% (RPHA). However, it was still relatively high at 8.38% in new army recruit blood donors, while in the general population it had decreased to 6.75%. The data suggested that carriers were more likely to be found in new army recruit blood donors, because most of them are from lower socioeconomic groups, less well educated, from rural areas and sexually active. Therefore, the immunization against hepatitis B must be considered for this high risk group in order to reduce the number of hepatitis B carriers.

Risk of transfusion associated AIDS by seronegative blood in Thailand: a multicenter report.

Prevention of transfusion associated AIDS (TAA) in Thailand began in 1986 when the HIV infection started to be sharply increased among the general population. The retrospective anti-HIV screening in various blood donor populations by The National Blood Center (NBC) revealed a seroconverted prisoner. Then the use of prisoners, prisoners' blood was not recommended from 1986. In April 1987, the first case of TAA was disclosed. Five months later, anti-HIV screening in all units of blood was firstly introduced at Ramathibodi Hospital (RH) and NBC. From 1989, anti-HIV screening in all units of blood is mandatory nationwide by Ministry of Public Health. Despite the anti-HIV screening, TAA cases transmitted by seronegative blood were gradually reported. Among many Medical Centers, there were 9 and 18 cases of TAA recorded from Chiang Mai and Bangkok areas respectively, since 1985. In addition, several new seroconverters were observed among voluntary blood donors. All of this evidence indicates the existence of blood donation during the early stage of infection, the so-called "window period". At present, HIV-P24 antigen ELISA seems to be the only available technique for mass screening. In 1990, NBC successfully performed a retrospective study on HIV-Ag ELISA screening by obtaining the prevalence of 1/10,000 units of blood. At the same period of time, in RH prospective study, a unit of blood with HIV-Ag only was detected when 3432 units of blood were screened. The HIV-Ag ELISA screening was then performed on every unit of blood routinely since Aug 12, 1991 at RH.(ABSTRACT TRUNCATED AT 250 WORDS)