Seroepidemiology of human hydatidosis: use of dried blood samples on filter paper

Programmes for the control of hydatidosis caused by Echinococcus granulosus in Argentina use an enzyme immunoassay (EIA) as a screening test for population surveys aimed at detecting asymptomatic patients. Persons thus selected are referred to health centres for the arc 5 double diffusion test and imaging techniques. One of the most costly procedures of these surveys is the collection of blood samples under field conditions; the possibility of collecting dry blood samples on filter paper was therefore investigated. In a survey of 497 rural inhabitants of an endemic area, the same number of hydatidosis cases (22) were identified by EIA using (i) serum samples and (ii) capillary blood samples obtained by finger prick and collected on filter paper. The latter system was both simpler and cheaper.     

Use of filter paper stored dried blood for measurement of triglycerides

Adaptation of assays on dried blood has advantages of ease of collection, transportation, minimal invasiveness and requirement of small volume. A method for extraction and estimation of triglyceride from blood spots dried on filter paper (Whatman no. 3) has been developed. A single dried blood spot containing 10 μL blood was used. Triglyceride was efficiently extracted in methanol from blood dried on filter paper by incubation at 37°C for two hours with gentle shaking. For the estimation, a commercially available enzymatic method was used. Blood spot assays showed mean intra and inter assay coefficient of variance of 6.0% and 7.4% respectively. A comparison of paired whole blood spots and plasma samples (n = 75, day 0) gave an intraclass correlation of 0.96. The recovery was 99.6%. The dried blood triglyceride concentrations were stable for one month when the filter discs were stored at room temperature (16–28°C). Storage of filters at 4°C extended the stability and triglycerides could be quantatively recovered after 3 months of storage.     

Screening of folate status with use of dried blood spots on filter paper.

BACKGROUND: Dried blood spots (DBS) on filter paper have been a successful and economical matrix for neonatal screening. OBJECTIVE: Our objective was to develop and evaluate an optimized method for DBS folate analysis and to assess DBS folate stability. DESIGN: DBS were eluted from paper by sonication in 5 g ascorbic acid/L containing 0.1% (by vol) Triton X-100 and hemoglobin folate values (HF; as pmol/g) were calculated from DBS eluate folate and hemoglobin concentrations. RESULTS: Over 95% of DBS folate was eluted during a standardized sonication cycle and DBS folate assay reproducibility was acceptable both within (CV: <8%) and between (CV: <9%) runs. HF means (+/-1 SD) from finger-stick DBS and conventional venous methods were 2513 +/- 1144 and 2607 +/- 1195 pmol/g, respectively, in blood samples taken concurrently from 80 donors, and they correlated well (r = 0.97, P < 0.001). HF values and erythrocyte folate measures may be interconverted by using the mean cell hemoglobin concentration. CONCLUSION: The DBS matrix has potential as an inexpensive and practical option for folate screening studies.     

Testing for mutagens in filter samples from the work atmosphere of an aluminum plant

Filter extracts of airborne particles from a S?derberg potroom and an anode paste plant were tested for mutagenicity by the Salmonella reversion assay. The extracts were mutagenic to strains TA100 and TA98, mainly after metabolic activation, but positive results were obtained also without S9 mix in strain TA98. These findings indicate that the particulate phase of air from the potroom and the anode paste plant of aluminum plants contain mostly indirect mutagens of both the base-pair substitution and frameshift type, and--to a less degree--frameshift mutagens. The relationship between concentration and mutagenicity was more positive for the potroom extract than for the anode paste plant extract.     

Seroepidemiology of HTLV-I in relation to that of HIV-1 in the Gauteng region, South Africa, using dried blood spots on filter papers.

The seroprevalence of human T-lymphotropic virus type I (HTLV-I), in relation to that of human immunodeficiency virus type I (HIV-1), was determined in a comparative unlinked anonymous antenatal and neonatal (for indirect measurement of maternal antibodies) serosurvey in the Gauteng region of South Africa, using dried blood spots (DBS) and modified particle agglutination assays. Samples were confirmed to be antibody positive by western blot. A total of 2582 DBS collected during 1993 and 1994 from subjects of African, European and coloured origin were tested. Ten were confirmed as positive for HTLV-I and 128 for HIV-1. No antibodies to HTLV-I or HIV-1 were demonstrated in the 221 women of European and coloured origin who were screened. The HTLV-I seroprevalence rate in subjects of African origin appeared to increase from 0% in 1993 to 0.49% in 1994, while HIV-1 seroprevalence rates of 5.2% and 5.4% were recorded for 1993 and 1994 respectively. No significant differences in HTLV-I and HIV-1 seroprevalence rates were noted for the two areas investigated. These results indicate that HTLV-I should be included in infection control programs, and provide baseline data for monitoring the possible spread of HTLV-I in the heterosexual population in this region.     

纸血片AFP及β-HCG检测用于唐氏综合征的产前筛查

目的检测纸血片中AFP及Β-HCG,探讨该方法用于唐氏综合征产前筛查的可行性。方法采用标准双抗体夹心ELISA方法检测AFP及Β-HCG,对164例不同孕周孕妇纸血片及血清标本同时进行对比试验。结果血清与纸血片2种方法的相关系数>0．92,呈高度相关。根据2种方法检测结果,通过优普生软件计算各标本的危险系数,以<1／500为需进一步进行相应检查的高危人群,2种方法检测均为高危人群者14例,均为非高危人群145例,2种方法一致总例数为98．9％(159／161),其中2例不符,均在临界值附近。血片稳定性好,在4℃贮存3个月后检测AFP和HCG,其回收率分别为100．4％和94．2％,批内变异系数(CV)<10％,批间VC <15％。结论测定纸血片中AFP及Β-HCG与用血清进行检测结果一致性高,都可用于唐氏综合征产前筛查。     

Evaluation of Testryp CATT applied to samples of dried blood for the diagnosis of sleeping sickness.

Described is an evaluation of the card agglutination test (Testryp CATT) applied to dried blood collected on filter-paper. The sensitivity of the test was compared for samples of diluted sera, whole blood and dried blood. Sera diluted 1:8 gave similar CATT results to those obtained with dried blood. The false negative rate was 5.8%, and test specificity, 100.0%. Use of CATT with samples of dried blood is recommended for screening populations at risk for trypanosomiasis in situations where specialized surveillance teams are not available to test sera or whole blood.     

Measurement of diphtheria and tetanus antitoxin in blood samples collected on filter paper disks.

Large-scale surveys of immunity to vaccine-preventable diseases may be limited by the inconvenience and expense involved in collection of blood by venepuncture. An alternative method of collecting blood on filter paper for measurement of immunity to diphtheria and tetanus is described. The precut filter disks (Elisadiscs), originally developed for serological diagnosis of disease in pigs, have advantages over previously described methods in that they allow safe handling of minimal volumes of blood (5 microliters) which can be conveniently quantified. To compare values obtained by venepuncture and fingerprick, paired samples were collected from 60 subjects and diphtheria and tetanus antitoxin concentrations were measured by ELISA. There was no significant difference detected between samples collected by the two methods. The results suggest that Elisadiscs are a reliable alternative to venepuncture for monitoring immunity to diphtheria and tetanus and would be useful for sample collection in remote areas and from children.     

Inter-test reliability of the anti-RESA indices based on ELISA tests using eluates from whole blood spots dried on filter paper

The ring-infected erythrocyte surface antigen (RESA), is one of the falciparum malaria vaccine candidates rarely studied in Brazil. Fieldwork logistics to conduct serology studies is simplified when eluates from whole blood dried on filter paper can be used. Therefore, this study aimed to assess the inter-test reliability for the anti-RESA ELISA-based indices using eluates from filter paper and from serum samples. The study population consisted of 210 individuals (Brazil) from whom matched samples were collected. Anti-RESA ELISA-based index means (+/- S.D.) were 15.29% (+/-28.13%) for filter paper and 11.79% (+/-23.67%) for serum samples. The intra-class correlation coefficient was estimated to be 82.38%, indicating high test reliability. However, there was a significant tendency for filter paper test results to have higher values than serum sample test results (P < 0.001). Explanations for this finding may be the presence of haemoglobin in the eluates from filter paper, which may interfere with ELISA testing.     

Maternal antibody to hepatitis B core antigen detected in dried neonatal blood spot samples.

Despite Department of Health recommendations, universal antenatal testing for hepatitis B virus (HBV) is not performed throughout Scotland. We describe the evaluation of an assay to document past or present infection with HBV, by identifying maternal antibody in routine Guthrie dried neonatal blood spot samples taken when infants are 7 days old. A modified haemagglutination assay to detect antibody to hepatitis B core antigen (CORECELL, Green Cross) was validated and found to be 79% sensitive (44/56) and 100% (105/105) specific when used with dried blood spot samples made from panels of serum of known reactivity. Ninety-three percent (13/14) of HBV carriers were CORECELL positive. Sixty-six (0.5%) of 14044 routine Guthrie samples taken from babies born in Scotland from June August 1992 were CORECELL positive indicating past or present maternal infection with HBV. A cross-sectional survey would document the maternity hospitals where universal antenatal hepatitis B screening should be urgently established.     

Detection of antibodies against hepatitis A in blood spots dried on filter paper. Is this a reliable method for epidemiological studies?

Diluted dried blood drops on filter paper were compared with serum samples as a specimen source for qualitative anti-HAV antibody determination by ELISA. A total of 298 serum samples and dried blood drops were collected from a population of healthy adolescents (15.3 +/- 1.2 years old). The prevalence of anti-HAV antibody obtained by testing serum samples was 7.7% (95% CI:4.8 10.1). Compared with serum sampling the sensitivity and specificity of diluted dried blood drops were 91.3 and 99.3%. The positive and negative predictive values were 91.3 and 99.3%, respectively, and the likelihood ratios of positive and negative results were 91 and 0.09. It is proposed that this test represents a reliable procedure for anti-HAV antibody testing.