Evaluation of blood collected on filter paper for detection of antibodies to human immunodeficiency virus type 1

What a drop can do: dried blood spots as a minimally invasive method for integrating biomarkers into population-based research

Logistical constraints associated with the collection and analysis of biological samples in community-based settings have been a significant impediment to integrative, multilevel bio-demographic and biobehavioral research. However recent methodological developments have overcome many of these constraints and have also expanded the options for incorporating biomarkers into population-based health research in international as well as domestic contexts. In particular using dried blood spot (DBS) samples-drops of whole blood collected on filter paper from a simple finger prick-provides a minimally invasive method for collecting blood samples in nonclinical settings. After a brief discussion of biomarkers more generally, we review procedures for collecting, handling, and analyzing DBS samples. Advantages of using DBS samples-compared with venipuncture include the relative ease and low cost of sample collection, transport, and storage. Disadvantages include requirements for assay development and validation as well as the relatively small volumes of sample. We present the results of a comprehensive literature review of published protocols for analysis of DBS samples, and we provide more detailed analysis of protocols for 45 analytes likely to be of particular relevance to population-level health research. Our objective is to provide investigators with the information they need to make informed decisions regarding the appropriateness of blood spot methods for their research interests.

Feasibility of detecting human immunodeficiency virus type 1 drug resistance in DNA extracted from whole blood or dried blood spots

Due to high cost, availability of human immunodeficiency virus type 1 (HIV-1) drug resistance testing in resource-poor settings is still limited. We therefore evaluated the usefulness of viral DNA extracted from either whole blood or dried blood spots (DBS). Samples were collected from 50 patients receiving therapy and 10 therapy-naïve patients. Amplification and sequencing of RNA and DNA was performed using an in-house assay. Protease (PR) and reverse transcriptase (RT) sequences of plasma viral RNA were obtained for 96.6% and 89.7%, respectively, of the 29 patients with a detectable viral load. For cellular viral DNA, useful PR and RT sequences were obtained for 96.6% and 93.1% of the whole-blood-cell samples and for 93.1% and 93.1% of the DBS samples, respectively. For the 31 patients with an undetectable viral load, PR and RT sequences were obtained for 67.7% and 61.3% of the whole-blood-cell DNA preparations and for 54.8% and 58.1% of the DBS DNA preparations, respectively. A good correlation between RNA and DNA sequences was found; most discordances were caused by the detection of mixed amino acids. Of the RT drug-resistant mutations, 13 (38.2%) were seen in RNA only, 6 (17.6%) in DNA only, and 15 (44.1%) in both. Repeated amplification and sequencing of DNA extracts revealed a lack of reproducibility for the detection of drug resistance mutations in a number of samples, indicating a possible founder effect. In conclusion, this study shows the feasibility of genotypic drug resistance testing on whole blood cells or DBS and its possible usefulness for HIV-1 subtyping or examining the overall distribution of drug resistance in a population. For individual patients, RNA sequencing was shown to be superior to DNA sequencing, especially for patients who experienced early treatment failure. The use of DNA extracted from whole blood or DBS for the detection of archived drug resistance mutations deserves further study.

A simple method for collecting measured whole blood with quantitative recovery of antibody activities for serological surveys

Compliance and acceptance for the finger-prick method of blood collection is generally better than for venipuncture. A finger-prick method of blood collection with quantitative antibody recovery is even more important for seroepidemiological surveys. Finger-prick blood collected and dried onto filter paper has been used; but, unfortunately, this method has several disadvantages, including loss of antibody activity, possible contact contamination from blood spots on adjacent filter papers, and difficulties in extracting antibodies, justifying the search for other methods of collecting and transporting blood samples. We report on a simple method of collecting a measured amount of finger-prick blood onto a sample pad, which is immediately transferred to storage/extraction buffer. The diluted blood sample is never dried, and because of the storage buffer, can be transported and stored without refrigeration. Furthermore, the diluted blood samples can then be tested directly without further preparation. We systematically compared several storage/extraction buffers and commercially available filter papers. We showed that antibody recovery was not significantly affected by the type of filter papers used but was significantly affected by the storage/extraction buffer used. The best such buffer is StabilZyme Select.

A population-based study of human immunodeficiency virus in south India reveals major differences from sentinel surveillance-based estimates

BACKGROUND

The human immunodeficiency virus (HIV) burden among adults in India is estimated officially by direct extrapolation of annual sentinel surveillance data from public-sector antenatal and sexually transmitted infection (STI) clinics and some high-risk groups. The validity of these extrapolations has not been systematically examined with a large sample population-based study.

METHODS

We sampled 13838 people, 15-49 years old, from 66 rural and urban clusters using a stratified random method to represent adults in Guntur district in the south Indian state of Andhra Pradesh. We interviewed the sampled participants and obtained dried blood spots from them, and tested blood for HIV antibody, antigen and nucleic acid. We calculated the number of people with HIV in Guntur district based on these data, compared it with the estimate using the sentinel surveillance data and method, and analysed health services use data to understand the differences.

RESULTS

In total, 12617 people (91.2% of the sampled group) gave a blood sample. Adjusted HIV prevalence was 1.72% (95% confidence interval 1.35-2.09%); men 1.74% (1.27-2.21%), women 1.70% (1.36-2.04%); rural 1.64% (1.10-2.18%), urban 1.89% (1.39-2.39%). HIV prevalence was 2.58% and 1.20% in people in the lower and upper halves of a standard of living index (SLI). Of women who had become pregnant during the past 2 years, 21.1% had used antenatal care in large public-sector hospitals participating in sentinel surveillance. There was an over-representation of the lowest SLI quartile (44.7%) in this group, and 3.61% HIV prevalence versus 1.08% in the remaining pregnant women. HIV prevalence was higher in that group even when women were matched for the same SLI half (lower half 4.39%, upper 2.63%) than in the latter (lower 1.06%, upper 1.05%), due to referral of HIV-positive/suspected women by private practitioners to public hospitals. The sentinel surveillance method (HIV prevalence: antenatal clinic 3%, STI clinic 22.8%, female sex workers 12.8%) led to an estimate of 112635 (4.38%) people with HIV, 15-49 years old, in Guntur district, which was 2.5 times the 45942 (1.79%) estimate based on our population-based study.

CONCLUSION

The official method in India leads to a gross overestimation of the HIV burden in this district due to addition of substantial extra HIV estimates from STI clinics, the common practice of referral of HIV-positive/suspected people to public hospitals, and a preferential use of public hospitals by people in lower socioeconomic strata. India may be overestimating its HIV burden with the currently used official estimation method.

Comparison of available methods to elute serum from dried blood spot samples for measles serology

Six existing protocols for the extraction of serum from blood spots dried onto filter paper were compared. Assessment criteria included: detection of measles IgM and IgG by the Dade Behring Enzygnost immunoassays, volumes of recovered eluates, reproducibility, processing time and throughput, difficulty of protocol, equipment required, safety and estimated costs. Detection of measles IgM in eluates obtained by four of these protocols was as in serum, and significant differences were only observed in eluates from the two remaining protocols (p < 0.05). Significant differences were found between extraction protocols regarding measles-specific IgG detection when an IgG indeterminate DBS was analyzed (p < 0.05), but not when an IgG positive and negative DBS were studied. Sufficient eluate volumes were recovered for testing in the IgM Behring assay following all protocols but two. Sufficient eluate was recovered for testing in the IgG Behring assay following all six protocols. While all protocols were relatively easy to perform, only two protocols required less than 2h for completion. In general, compared protocols performed well on the extraction of antibodies from DBS for serology with differences being observed with eluate volume recovery, turn around time, required equipment and cost. An easy-to-implement protocol is proposed for the rapid extraction of serum for measles/rubella serology in outbreak situations for use in the World Health Organization Global Measles and Rubella Laboratory Network.

Whole blood samples as an alternative to serum for detection of immunity to measles virus by ELISA

The aim of this study was to evaluate enzyme linked immunosorbent assay (ELISA) as a testing strategy for detection of antibodies against measles virus from microquantities of blood soaked onto filter paper. We studied 165 healthy children in the age group of 1 to 2 years, attending the outpatient department of pediatrics. Two sets of samples were collected from each child. One by venipuncture and the other on Whatman filter paper-3 discs of 20 mm size by finger or heel prick so that each strip is completely soaked with blood on both sides. These were tested for measles virus antibodies by ELISA using Melotest measles IgG commercial ELISA kit manufactured by Melotec S. A. (Barcelona, Spain). The resulting sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the filter paper (FP) ELISA compared to serum ELISA was 100, 90, 97.8, and 100%, respectively. The correlation coefficient r = 0.93% (p < 0.001) and the agreement between the two techniques was 98% as calculated by the Kappa statistical method. The present study has found filter paper testing by ELISA to be a promising qualitative technique for detection of immunity against measles.

Neurocysticercosis: validity of ELISA after storage of whole blood and cerebrospinal fluid on paper

Cysticercosis is an infestation of Cysticercus cellulosae. When it occurs in the brain, chronic neurological complications can ensue, most commonly seizures. Neurocysticercosis is usually diagnosed by neuroimaging, a technique not available in most endemic countries. Hence immunological tests are valuable for diagnosis and epidemiological surveys. We evaluated the suitability of paper for storing blood and cerebrospinal fluid (CSF) until subsequent testing by enzyme-linked immunosorbent assay (ELISA), by testing whole blood samples on filter paper from 305 patients and CSF samples from 117 patients stored on ordinary white typing paper and on filter paper. Optimal preservation of biological samples is achieved when whole blood is stored on filter paper, CSF on white paper, and when samples are frozen within 1 week after collection. Our results could improve diagnostic capabilities and facilitate epidemiological surveys in endemic countries where immunodiagnostic tests cannot be rapidly performed because of inadequate laboratory infrastructure.

The use of the dried blood spot sample in epidemiological studies

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Detection of immunoglobulin G to measles virus, rubella virus, and mumps virus in serum samples and in microquantities of whole blood dried on filter paper

Immunity to measles virus, rubella virus, and mumps virus was determined by EIA in serum samples and in dried whole blood specimens spotted on Whatman filter paper (5 mm in diameter). Both specimens were obtained from each patient by venepuncture and finger prick. Ten microliters of whole blood is enough to detect antibodies to these three different viruses. The comparison of the results obtained by EIA from 227 serum and whole blood samples have demonstrated close agreement: 98.6% for measles virus, 99.1% for rubella virus, and 96.0% for mumps virus. Moreover, 96 whole blood samples can be tested in a microtiter plate and can be stored at room temperature for 15 days or at +4 degrees C for several months. Therefore, whole blood dried on filter paper is a convenient alternative method for collecting and transporting specimens, it is easier and safer than venepuncture, and could be used for large-scale epidemiological studies, especially in newborns. This method could solve the problem of sampling, especially in young children, and could simplify studies of vaccine efficacy.

Factors influencing HIV-1 banding patterns in miniaturized western blot testing of dried blood spot specimens

In the HIV Seroprevalence Survey among Childbearing Women (SCBW), antibodies to human immunodeficiency virus type 1 are detected using enzyme immunoassays (EIA) and Western blot (WB) methods modified to accommodate samples of blood dried on special collection paper. Dried blood spot (DBS) eluates positive by EIA are tested by one of two WB methods, the miniblot technique using equipment from Immunetics Corporation and the PBS Integra assay (pageblot) from Genetic Systems. In this report we compared the performance of the two WB methods. The identity and position of the viral proteins on the WB were identified using monoclonal antibodies and monospecific antisera. The blots differed substantially in their composition and concentration of viral glycoproteins. Performance of the WB assays with DBS elution buffers from different EIA kits was equivalent except for samples eluted in the Abbott buffer, which reduced detection of antibodies to the p31, p51, p55, and p66 viral proteins. Case classification of DBS, positive sera, dilution curve samples, and seroconversion panels was equivalent by both tests in the presence of all elution buffers. Proficiency evaluation panels sent to SCBW participating laboratories over a 3-year period were used to note the differences between the two WB methods in detection of antibodies to the viral glycoproteins.

HIV risk behaviour among injecting drug users in Perth: the Australian National AIDS and Injecting Drug Use Study

OBJECTIVE

This study was carried out in 1989 to examine behaviour involving risk of human immunodeficiency virus (HIV) infection and to measure the prevalence of HIV antibodies in a sample of injecting drug users (IDUs) in Perth.

DESIGN

The study was a cross-sectional survey with a sample of convenience of 196 IDUs drawn from drug treatment (54%) and non-treatment (46%) populations.

RESULTS

Sixty-five per cent of the sample were men and 35% women. Subjects were predominantly heterosexual, were in their late twenties, had not completed secondary school, and were on sickness, unemployment or pension benefits. The majority were poly-drug users, but heroin and amphetamines were the only drugs that had been injected by more than 20% of the sample more than once a month. Respondents reported injecting an average of 43.6 (SD 83.6) times a month and using 33.7 (SD 55.4) new needles a month. The majority (70%) had injected within weeks of the interview. Sixty-seven per cent had shared needles within months. Respondents claimed to pass on used needles more frequently than to accept them, and were most likely to share with close friends or lovers when clean needles were unavailable and/or when they were withdrawing. While most respondents cleaned used needles, few used bleach all or most of the time. Most (78%) respondents had been tested for HIV seropositivity at least once. Most had multiple sexual partners and 92.3% had engaged in at least one unsafe sexual practice during the previous six months. Sixty-four per cent had changed some aspect of drug using, and 38% some aspect of sexual behaviour since hearing about the acquired immunodeficiency syndrome (AIDS). HIV seroprevalence for the 179 respondents who were tested was 2.2%, but this figure should not be taken as an estimate of seroprevalence for the Perth IDU population.

CONCLUSION

Respondents' behaviour placed them at a high level of risk for HIV infection. Based on reported behaviour, it is recommended that education for IDUs in Perth should emphasise, among other things: not passing on used needles; cleaning used needles and syringes with bleach; planning ahead so that sterile equipment is available; and further risk reduction, particularly the adoption of safer sexual practices.

Evaluation of the Genetic Systems Corp. Integra HIV-1 Pageblot system

The Genetic Systems Corp. Integra HIV-1 Pageblot system was evaluated as a supplementary assay to confirm the presence of antibodies to human immunodeficiency virus type 1 in 57 specimens from individuals at high risk of infection with the virus. Forty-one specimens identified as reactive in the Genetic Systems Integra HIV-1 Pageblot system were likewise identified as reactive in a U.S. Food and Drug Administration-licensed (Biotech/Dupont) Western blot (immunoblot). Six specimens identified as indeterminate in either or both immunoblot assays were all identified as nonreactive in a U.S. Food and Drug Administration-licensed enzyme immunoassay with recombinant antigens.

Use of a silver-enhanced gold-labelled immunoassay for detection of antibodies to the human immunodeficiency virus in whole blood samples

A silver-enhanced gold-labelled immunosorbent assay (SEGLISA) for the detection of antibodies to the immunodeficiency virus (HIV) in whole-blood samples is described. This new non-isotopic, non-enzymic immunoassay incorporates use of solid phase viral antigens which bind any HIV antibodies present in the test sample. The antigen/antibody complex is then detected by gold-labelled anti human immunoglobulin G (IgG) followed by silver amplification. We found that whole blood samples give false positives when using a horseradish peroxidase label, whereas the SEGLISA correctly identified 50 HIV antibody positive samples and 50 HIV antibody negative samples when using whole blood. The use of whole blood collected on filter paper is also described. The SEGLISA has good precision (CV = 7.5%) and sensitivity.