One hundred and twenty one sera were used for efficiency comparison between the rubella test kit produced by Department of Medical Sciences (Rub-HAl kit,DMS) and the commercial kit (Rube-HIT, Behring). The qualitative determination of rubella antibodies in sera showed that the sensitivity, specificity, positive predictive value, negative predictive value and efficiency of Rub-HAl kit were 92.4%, 100%, 100%,78.6% and 94.1%. respectively. A number of patients with recent rubella. infections were also investigated,and it was found that the accuracy of test kit was comparable to that of the commercial one. In terms of the diagnostic cost, Rub-HAl kit was much lower about thirty-five times less. So the rubella lest kit produced by Department of Medical Sciences is suitable and very useful for health services of the Ministry of Public Health.

To support the surveillance system of dengue hemorrhagic fever, paired blood collected on filter papers were submitted form hospitals all over the country to the Department of Medical Sciences for laboratory confirmation. During 1986 to 1989, samples from 27.288 DHF suspected patients (9.0% of the total reported cases) were examined using HI test and antibody capture ELISA. The dengue infection serologically proved throughout the 4 year study was 65.8%. Outside epidemic period (December to March) samples from 9.8% of the reported cases were tested and 68.7% were confirmed for dengue infection. During epidemic period (April to November), 8.9% of the reported cases were tested and 65.6% were confirmed. Distribution of the estimated dengue infected patients by months, regions and age groups showed close relation with those of the total reported cases. Peek incidences of dengue infected cases were in September 1986 and in July in 1987-1989. During December 1986 to March 1989, the usual dengue infected patients were unusual high that followed by the largest outbreak of DHF in 1987. The data indicated the highest number of dengue infected patients in the central region in 1986, whereas in 1987 the very high incidences were found in every region. The epidemics in 1988 and 1989 occurred mostly in the northeast. The majority of dengue confirmed cases was in the age group 5-9 years with the next most common age group being l0 to 14 years. An increasing trend to the higher age groups was observed. Of the total, 83.5% of dengue confirmed cases experienced secondary infection which was the least found in the age group under one year (39.5%). Among the patients with clinical diagnosis of DHF recorded in the request forms, 70.l% were dengue infection confirmed, while among the patients with fever of unknown origin, only 56.9% were confirmed. This study provides definite information for the planning and evaluation of DHF control. Key words: Dengue Hemorrhagic Fever, Dengue infections, Laboratory diagnosis

A dot immunoassay was evaluated for its efficacy in diagnosis of HIV-infection. 328 sera were analyzed to be 254 sero positive sera were found positive while 66 sero negative sera were negative. Therefore, this commercial kit gave sensitivity of 92.9% and specificity of 89.2% with predictive positive value and predictive negative value of 96.7% and 78.6%, respectively. Moreover, this method showed high variability of the observed data even when the results were observed by well-trained for diagnosis and selected for some risk groups. However, this method was not suitable for blood donors screening which required a higher performance of the test. ไดประเมนประสทธภาพของวธ Dot Immunoassay ในการตรวจวนจฉยการตดเชอเอชไอวทผานการตรวจวนจฉยยนยนจำนวน 328 ตวอยางทตรวจพบบวกดวยวธ Western blot จำนวน 254 รายและลบ 74 ราย พบวา วธนใหผลบวกกบซรมชนดบวกเพยง 236 ราย คดเปนความไวในการตรวจเพยงรอยละ 92.9 เมอตรวจซรมชนดลบกใหผลลบเพยง 66 ราย คดเปนความจำเพาะเพยงรอยละ 89.2 เทานน คาทำนายผลบวกและคาทำนายผลลบคดเปนรอยละ 96.7 และ 78.6 ตามลำดบ นอกจากนวธ Dot Immunoassay นยงมความแปรปรวนในการอานผลการทดสอบมากแมผอานผลจะเปนนกวทยาศาสตรการแพทยผชำนาญกตาม คณะผวจยเสนอใหใชวธนอยางระมดระวงและใชใหเหมาะสมกบกลมตวอยาง และไมควรใชวธนกบการตรวจคดกรองผบรจาคโลหตซงตองการวธทมความไวและความจำเพาะสงกวาน

The percentage of HIV-1 subtype E and subtype B were studied in HIV-1 infected mothers who delivered at Chiang Rai Regional Hospital Center and injecting drug users (IDU) from Thanyarak Narcotics Hospital, Pathumthani, During 1994-1995. The subtypes were analyzed by a peptide binding enzymeimmunoassay (PEIA) using specific synthetic peptides of 14 amino acid derived from V3-loop of gp 120. Of those 111 HIV-1 infected mothers, 109 (89.2%) were infected by HIV-1 subtype E while 2 (1.8%) were infected by HIV-1 subtype B. When 141 IDU were analyzed, 67 (47.5%) were infected by subtype E and 74 (52.5%) were infected by subtype B. These results showed that subtype E was predominant in the mothers who acquired HIV-1 infection via heterosexual transmission. However, in IDU, both subtypes were nearly equal and the percentage of subtype E in this group was slightly higher. Such data may indicated that the distribution of HIV-1 subtype E and subtype B in IDU, now, is near equilibrium. This postulation has to be kept on surveillance and further investigations are needed.

To study the distribution and level of infection by Rodent-borne diseases in reservoirrodent species in selected provinces from every regions in Thailand, a survey was conductedduring October 1998 to April 2000. The total rodent serum of 1,164 samples, which collectedfrom 10 provinces, were diagnosed for leptospirosis and found 4.8 per cent positive. The resultof 1,125 samples of rodent serum for scrub typhus test were reportedly 22.4 per cent positive.The nation wide 862 samples for hantavirus test reported only 2.9 per cent positive. The levelof infection by leptospira in reservoir rodent species were 6.9, 5.0, 2.6, 3.5 and 2.3 per cent inRattus exulans, R. rattus, R. norvegicus, Bandicota indica and B. savilei respectively. ForOrientia tsutsugamushi, they were 5.6, 29.2, 31.4, 25.7 and 32.1 per cent in R.exulans, R rattus,R. norvegicus, B. indica and B. savilei respectively. And for hantavirus, the infection rates were2.7, 2.4, 5.5 and 1.9 per cent in R. rattus, R. norvegicus, B. indica and B. savilei respectively.The highest evidence of leptospira infection were shown in the northeast, Buri Ram province.That of O. tsutsugamushi infection was found in the central part, Ayutthaya province. Theresults of endoparasite diagnosis of 1,767 samples of rodent internal organ for intestinal parasitewere reportedly 27.2 per cent positive and there were 10 species that can be transmitted toman with high density only 3 species. The examination confirmed the presence of blood parasitesin 6.1 per cent of the samples and there was only 1 species that can be transmitted to man.

Human immunodeficiency syndromes (AIDS) and hepatitis B are major public health problems in Thailand today, especially AIDS is rapidly spreading from risk groups to general population by sexual behviour. This study aims to determine prevalence of HIV-1 and hepatitis B infection among pregnant women attending the antinatal care clinic in Yodse hospital; a private hospital in Bangkok, during January 1993 - June 1995. This study shows 2,423 pregnant women had anti HIV-1 0.6% and HBs Ag positive 6%. The prevalence of HIV-1 infection by year was increased rapidly from 0.3% in 1993 to 0.7% and 1.3% in 1994 and 1995 respectively but hepatitis B infection (HBsAg) was steady from 5.6% in 1993 to 6.5% and 6.0% in 1994 and 1995 respectively. Both infections were highest in group 20-29 years old. The study provides the base line data in middle class pregnant women who rather had good economic and education for planning to control the infection of these disesses.

An alternative strategy for HIV-1 seropositive confirmation test was studied using combination of two or three screening tests. Four commercially available screening tests: (three ELISA tests and one agglutination assay) were evaluated. There were 620 HIV-1 seropositive sera collected from Phayoa Hospital and many hospitals in the central region of Thailand. It was found that all four tests could not reveal 100% accuracy compared to Western blot analysis. There were 9 combination of 2 or 3 screening tests as an alternative confirmatory strategy which could assure not only the positive cases, but also indicate the indeterminate ones. This alternative test might be beneficial to laboratories in regional areas since it offered simpler, more rapid and less expensive protocol for HIV-1 confirmation.