Performance characteristics and costs of serological tests for brucellosis in a pastoralist community of northern Tanzania.

The control of brucellosis across sub-Saharan Africa is hampered by the lack of standardized testing and the use of tests with poor performance. This study evaluated the performance and costs of serological assays for human brucellosis in a pastoralist community in northern Tanzania. Serum collected from 218 febrile hospital patients was used to evaluate the performance of seven index tests, selected based on international recommendation or current use. We evaluated the Rose Bengal test (RBT) using two protocols, four commercial agglutination tests and a competitive enzyme-linked immunosorbent assay (cELISA). The sensitivity, specificity, positive predictive value, negative predictive value, Youden's index, diagnostic accuracy, and per-sample cost of each index test were estimated. The diagnostic accuracy estimates ranged from 95.9 to 97.7% for the RBT, 55.0 to 72.0% for the commercial plate tests, and 89.4% for the cELISA. The per-sample cost range was $0.69-$0.79 for the RBT, $1.03-$1.14 for the commercial plate tests, and $2.51 for the cELISA. The widely used commercial plate tests performed poorly and cost more than the RBT. These findings provide evidence for the public health value of discontinuing the use of commercial agglutination tests for human brucellosis in Tanzania.

Hospital-based evidence on cost-effectiveness of brucellosis diagnostic tests and treatment in Kenyan hospitals.

Hospitals in Kenya continue to use the Febrile Antigen Brucella Agglutination Test (FBAT) to diagnose brucellosis, despite reports showing its inadequacy. This study generated hospital-based evidence on the performance and cost-effectiveness of the FBAT, compared to the Rose Bengal Test (RBT).Twelve hospitals in western Kenya stored patient serum samples that were tested for brucellosis using the FBAT, and these were later re-tested using the RBT. Data on the running time and cost of the FBAT, and the treatment prescribed for brucellosis, were collected. The cost-effectiveness of the two tests, defined as the cost in US Dollars ($) per Disability Adjusted Life Year (DALY) averted, was determined, and a basic sensitivity analysis was run to identify the most influential parameters. Over a 6-month period, 180 patient serum samples that were tested with FBAT at the hospitals were later re-tested with RBT at the field laboratory. Of these 24 (13.3%) and 3 (1.7%) tested positive with FBAT and RBT, respectively. The agreement between the FBAT and RBT was slight (Kappa = 0.12). Treatment prescribed following FBAT positivity varied between hospitals, and only one hospital prescribed a standardized therapy regimen. The mean $/DALY averted when using the FBAT and RBT were $2,065 (95% CI $481-$6,736) and $304 (95% CI $126-$604), respectively. Brucellosis prevalence was the most influential parameter in the cost-effectiveness of both tests. Extrapolation to the national level suggested that an estimated $338,891 (95% CI $47,000-$1,149,000) per year is currently spent unnecessarily treating those falsely testing positive by FBAT. These findings highlight the potential for misdiagnosis using the FBAT. Furthermore, the RBT is cost-effective, and could be considered as the mainstay screening test for human brucellosis in this setting. Lastly, the treatment regimens must be harmonized to ensure the appropriate use of antibiotics for treatment.

A Low-Cost Micro-Volume Nephelometric System for Quantitative Immunoagglutination Assays.

Immunoassays have been widely used in scientific research and clinical diagnosis due to their versatile detection capability and high specificity. Immunoagglutination assays are kinds of immunoassay, which can simply and rapidly measure the concentration of analytes. In this work, we developed a low-cost micro-volume nephelometric system for quantitative immunoagglutination assays. We used off-the-shelf components to build the system, and the total cost of key components is only about 20 US dollars. The total detection volume in our system was as low as 3 µL, which could significantly reduce the reagent cost and required sample volume. We further evaluated the system performance via the immunoagglutination assay to measure the concentration of C-reactive protein, a plasma protein with levels rising in response to inflammation. The results demonstrated that our system could measure the concentration of analytes with relatively high sensitivity and precision within four minutes, and has high potential to be applied for clinical diagnostic tests.

Comparison of a commercial modified direct agglutination test and a commercial enzyme-linked immunosorbent assay for screening for antibodies against Toxoplasma gondii in naturally exposed domestic cats.

Domestic cats and other felids are definitive hosts for the zoonotic protozoan parasite Toxoplasma gondii. Serology is widely used in epidemiological studies conducted to estimate the proportion of domestic cats that have encountered the parasite. However, a limited number of such studies are available from some regions, including eastern parts of Europe and Russia. Various serological tests have been applied for T. gondii serology for feline samples. Seropositivity indicates previous exposure, and seropositive cats are presumed to have shed oocysts of the parasite earlier and to be chronically infected. In this study, we included a random sample of 200 sera and plasma samples from a larger sampling frame comprising samples from domestic cats from Estonia, where T. gondii is common. The samples, which had been previously screened for anti-T. gondii immunoglobulin G antibodies using a commercial modified direct agglutination test (DAT: Toxo-Screen DA; bioMérieux SA, Marcy-l'Étoile, France), were screened using a commercial enzyme-linked immunosorbent assay (ELISA: VectoToxo-antibodies [VektoTokso-antytila], VectorBest, Novosibirsk, Russian Federation). The cut-off for seropositivity with DAT was titer of 40. Of the 200 samples, 120 (60.0%) tested positive with DAT and 114 (57.0%) tested positive with ELISA; 112 samples (56.0%) tested positive with both tests. Percent agreement of 95.0% and Kappa 0.8971 indicated an almost perfect agreement between the screening results using the two methods. The results of this study can be useful for comparison, evaluation, and interpretation of results obtained with these two tests in seroepidemiological studies and may encourage more studies on the topic from eastern parts of Europe and Russia.

Whole-Cell Biosensor with Tunable Limit of Detection Enables Low-Cost Agglutination Assays for Medical Diagnostic Applications.

Whole-cell biosensors can form the basis of affordable, easy-to-use diagnostic tests that can be readily deployed for point-of-care (POC) testing, but to date the detection of analytes such as proteins that cannot easily diffuse across the cell membrane has been challenging. Here we developed a novel biosensing platform based on cell agglutination using an E. coli whole-cell biosensor surface-displaying nanobodies which bind selectively to a target protein analyte. As a proof-of-concept, we show the feasibility of this design to detect a model analyte at nanomolar concentrations. Moreover, we show that the design architecture is flexible by building assays optimized to detect a range of model analyte concentrations using straightforward design rules and a mathematical model. Finally, we re-engineer our whole-cell biosensor for the detection of a medically relevant biomarker by the display of two different nanobodies against human fibrinogen and demonstrate a detection limit as low as 10 pM in diluted human plasma. Overall, we demonstrate that our agglutination technology fulfills the requirement of POC testing by combining low-cost nanobody production, customizable detection range and low detection limits. This technology has the potential to produce affordable diagnostics for field-testing in the developing world, emergency or disaster relief sites, as well as routine medical testing and personalized medicine.

Cost-effectiveness of using a rapid diagnostic test to screen for human African trypanosomiasis in the Democratic Republic of the Congo.

New rapid diagnostic tests (RDTs) for screening human African trypanosomiasis (HAT) have been introduced as alternatives to the card agglutination test for trypanosomiasis (CATT). One brand of RDT, the SD BIOLINE HAT RDT has been shown to have lower specificity but higher sensitivity than CATT, so to make a rational choice between screening strategies, a cost-effectiveness analysis is a key element. In this paper we estimate the relative cost-effectiveness of CATT and the RDT when implemented in the Democratic Republic of the Congo (DRC). Data on the epidemiological parameters and costs were collected as part of a larger study. These data were used to model three different diagnostic algorithms in mobile teams and fixed health facilities, and the relative cost-effectiveness was measured as the average cost per case diagnosed. In both fixed facilities and mobile teams, screening of participants using the SD BIOLINE HAT RDT followed by parasitological confirmation had a lower cost-effectiveness ratio than in algorithms using CATT. Algorithms using the RDT were cheaper by 112.54 (33.2%) and 88.54 (32.92%) US dollars per case diagnosed in mobile teams and fixed health facilities respectively, when compared with algorithms using CATT. Sensitivity analysis demonstrated that these conclusions were robust to a number of assumptions, and that the results can be scaled to smaller or larger facilities, and a range of prevalences. The RDT was the most cost-effective screening test in all realistic scenarios and detected more cases than CATT. Thus, on this basis, the SD BIOLINE HAT RDT could be considered as the most cost-effective option for use in routine screening for HAT in the DRC.

Study of implementation and direct cost estimates for diagnostic tests for human visceral leishmaniasis in an urban area in Brazil / Estudo da implantação e estimativas de custo direto de testes diagnósticos para leishmaniose visceral humana em uma área urbana no Brasil / Estudio de la implementación y el costo directo estimado de pruebas de diagnóstico de la leishmaniasis visceral humana en una zona urbana en Brasil

Abstract This work reports the process and costs of comprehensively implementing two tests to decentralize the diagnosis of visceral leishmaniasis (VL) in an endemic city in Brazil: a rapid test (IT LEISH) and a direct agglutination test (DAT-LPC). The implementation began by training health professionals to perform the tests. Estimation of the training costs considered the proportional remuneration of all professionals involved and the direct costs of the tests used for training. The study was conducted between November 2011 and November 2013. During that time, 17 training sessions were held, and 175 professionals were trained. The training cost for each professional was US$ 7.13 for the IT LEISH and US$ 9.93 for the DAT-LPC. The direct costs of the IT LEISH and DAT-LPC were estimated to be US$ 6.62 and US$ 5.44, respectively. This first evaluation of the implementation of these diagnostic tests indicates the feasibility of decentralizing both methods to extend access to VL diagnosis in Brazil.

Resumo Este trabalho relata o processo e os custos da implantação de dois testes para descentralizar o diagnóstico da leishmaniose visceral (LV) em um município endêmico no Brasil: um teste rápido (IT LEISH) e um teste de aglutinação direta (DAT-LPC). A implantação iniciou com o treinamento dos profissionais de saúde do município na realização dos testes diagnósticos. Os itens incluídos nas estimativas de custo das capacitações foram a remuneração proporcional de todos os profissionais envolvidos e os custos diretos dos testes usados. O estudo foi conduzido entre novembro de 2011 e novembro de 2013. Durante esse período, 17 capacitações foram realizadas e 175 profissionais treinados. O custo relacionado a cada profissional de saúde capacitado na realização do IT LEISH foi de US$ 7,13 e na realização do DAT-LPC, de US$ 9,93. O custo direto do IT LEISH e do DAT-LPC foi estimado em US$ 6,62 e US$ 5,44, respectivamente. Esta primeira avaliação da implantação desses dois testes aponta para a viabilidade da descentralização de ambos os métodos, que aumentam o acesso ao diagnóstico da LV no Brasil.

Resumen Este trabajo relata la puesta en funcionamiento y los costos de pruebas de diagnóstico de VL en un municipio endémico en Brasil: el test rápido (IT LEISH) y la prueba de aglutinación directa (DAT-LPC). Esta puesta en marcha comenzó por capacitar al personal sanitario del municipio para la realización de las pruebas. Para estimar los costos de la capacitación, se consideró la remuneración proporcional de todo el personal involucrado y los costos directos derivados de la aplicación de las pruebas. El estudio fue realizado entre noviembre de 2011 y noviembre de 2013. En ese periodo se realizaron 17 capacitaciones y se formaron 175 profesionales. Se calcula que el costo derivado de capacitar cada profesional para realizar el IT LEISH fue de 7.13 US$ y 9.93 US$ para el DAT-LPC. Los costos directos del IT LEISH y del DAT-LPC se estimaron en 6,62 US$ y 5,44 US$ respectivamente. La primera evaluación de la puesta en funcionamiento de las dos pruebas en este municipio señala que es viable descentralizar su realización, lo que amplía el acceso al diagnóstico de la VL en Brasil.

Study of implementation and direct cost estimates for diagnostic tests for human visceral leishmaniasis in an urban area in Brazil.

This work reports the process and costs of comprehensively implementing two tests to decentralize the diagnosis of visceral leishmaniasis (VL) in an endemic city in Brazil: a rapid test (IT LEISH) and a direct agglutination test (DAT-LPC). The implementation began by training health professionals to perform the tests. Estimation of the training costs considered the proportional remuneration of all professionals involved and the direct costs of the tests used for training. The study was conducted between November 2011 and November 2013. During that time, 17 training sessions were held, and 175 professionals were trained. The training cost for each professional was US$ 7.13 for the IT LEISH and US$ 9.93 for the DAT-LPC. The direct costs of the IT LEISH and DAT-LPC were estimated to be US$ 6.62 and US$ 5.44, respectively. This first evaluation of the implementation of these diagnostic tests indicates the feasibility of decentralizing both methods to extend access to VL diagnosis in Brazil.

Screening of multiparous women to avoid transfusion-related acute lung injury: a single centre experience.

The aim of this study was to investigate which approach for serological testing of multiparous donors might be feasible and effective to reduce the risk of transfusion-related acute lung injury (TRALI). TRALI is a serious adverse event of blood transfusion. Antibodies to granulocytes and human leucocyte antigens (HLAs) are frequently detected in sera of implicated donors. These donors are often multiparous women. A general deferral of female plasma or screening strategies for leucocyte antibodies has been proposed to increase blood safety. A prospective study was initiated in 2003. Until 2006, serum samples from all female donors reporting three or more pregnancies (n = 229) were screened for the presence of antibodies against granulocytes and HLAs by immunofluorescence and agglutination tests as well as by a commercial HLA enzyme immunoassay. In total, 40% of all multiparous women were reactive in one of the assays. Twenty-nine percent of the reactive sera contained antibodies to granulocytes but not to HLAs. During the observation period, three TRALI reactions occurred in our hospital, two of which would have been prevented if the screening program had been extended to all previously pregnant donors. We conclude from these data that, not unexpectedly, the number of previous pregnancies is not a reliable indicator for the likelihood of inducing TRALI. More importantly, screening strategies for antibodies that might induce TRALI should probably not be reduced to HLA antibody screening. This finding awaits further research.

Evaluation of serodiagnostic tests for T.b. gambiense human African trypanosomiasis in southern Sudan.

A survey was conducted in a low-endemic and in a non-endemic area of Sudan to evaluate the specificity and efficiency of different serological antibody detection techniques for Trypanosoma brucei gambiense. Comparisons were made of the card agglutination test for trypanosomiasis (CATT) on diluted blood, on diluted plasma and on eluates from blood dried on filter paper, the LATEX test on diluted plasma and an ELISA on diluted plasma and filter paper. The specificities of all the serological tests were not significantly different from CATT on diluted blood (99.5%). The specificity of CATT on diluted blood was similar (99.3%). The highest sensitivities (100%) were observed with CATT on diluted blood and with CATT and LATEX on diluted plasma. CATT on diluted blood was more cost-efficient than the classic test, CATT on whole blood.

A new in-vitro agglutination technique for potency estimation of antisnake venom serum (ASVS).

Traditionally the potency of ASVS is assayed quantitatively by in-vivo neutralization test for lethality in mice. A sensitive and simple in-vitro agglutination assay for the quantitative determination of Antisnake Venom Serum (ASVS) potency is reported. The method is rapid, cheap, simple, economical and above all does not require the use of experimental animals for potency assay of in process, unpurified and purified sera batches. Among in-vitro procedures, agglutination assay was favored in comparison to flocculation as the later was found to give variable results and also time consuming (high Kf value). Before application, the method was standardized and validated for choice and concentration of particulate material (latex vs. bentonite), temperature and optimum antiserum concentration. It is well known fact that venoms lose toxicity on dilution however this study demonstrated that the bentonite adsorbed venoms of the entire four snake species viz., Cobra, Krait, Russell's viper and Echis are stable even up to 30 days of storage. Among five lots each of unpurified serum, unprocessed plasma and purified sera tested, the results were found comparable with universally accepted in-vivo biological assay. The coefficient of correlation was found to be near 1.0 within 95% fiducial limits of acceptance and also significantly less variation was observed in the mean potency values and standard deviations. For all results p value was observed to be <0.01. Results indicate that in-vitro agglutination assay is suitable and can be used for potency estimation of in process as well as unpurified and purified ASVS batches.

[The efficiency of different detection strategies of human African trypanosomiasis by T. b. gambiense]. / Efficience de differentes strategies de detection de la Trypanosomiase Humaine Africaine aT. b. gambiense.

INTRODUCTION: Population screening for human African trypanosomiasis (HAT) is often based on a combination of two screening tests: lymph node palpation (LN) and card agglutination test for trypanosomiasis (CATT). This decision analysis compared the efficiency of three alternative detection strategies: screening by LN only, CATT only and their combination (LN and CATT). METHOD: An HAT detection strategy was defined as the sequence of screening and confirmation. Efficacy was evaluated in terms of lives saved. The cost of screening and confirmation tests was estimated in US$. The different parameters in the decision tree were based on published literature and observations of the HAT control programme in the Democratic Republic of Congo. A sensitivity analysis was carried out on those parameters subject to uncertainty. RESULTS: The cost-effectiveness of a detection strategy based on CATT was US $125 per life saved, compared with US $517 for LN and US $452 for the combined. Marginal cost to add LN to CATT only was between US $1225 and US $5000 per life saved. Sensitivity analysis shows that these results are robust to variation. DISCUSSION: The CATT strategy was the most efficient. None of the strategies was able to avoid more than 60% of HAT deaths. This moderate efficacy is due to the low sensitivity of the confirmatory (diagnostic) tests. Substantial efficiency gains can be obtained by adopting a CATT only strategy and resources can be better allocated to more sensitive confirmatory tests or to increasing the coverage of populations at risk.

Serological diagnosis of bovine brucellosis: a review of test performance and cost comparison.

The authors reviewed over 50 publications in which the sensitivity and specificity values of assays used for the detection of exposure to Brucella abortus had been examined. The sum of the sensitivity and specificity values for each test was averaged to give a performance index (PI) and allow for a comparison between the different methodologies. A score of 200 was perfect. Based on the PI, the buffered antigen plate agglutination test (BPAT) rated highest (PI = 193.1) among the conventional tests. This indicates better accuracy than the other conventional tests including the Rose Bengal test (PI = 167.6) and the complement fixation test (PI = 172.5). Overall, the primary binding assays, including the fluorescence polarisation assay (PI = 196.4), the indirect enzyme-linked immunosorbent assay (PI = 189.8) and the competitive enzyme-linked immunosorbent assay (PI = 188.2), were more accurate than the conventional tests, except for the BPAT. In addition, a fee comparison suggested that the primary binding tests were price competitive with conventional tests for the diagnosis of brucellosis and, therefore, had a better combined cost/efficiency rating.

Validation of a simple and cheap gelatin particle agglutination test for human immunodeficiency virus using dried blood spot samples.

OBJECTIVES: To validate a Gelatin Particle Agglutination (GPA) test for HIV using dried blood spots with a view to applying the test in large epidemiological studies. DESIGN: A method comparison study with standard enzyme linked immunosorbent assay (ELISA) using the Recombigen HIV-1/2 kit as the gold standard. SETTING: Blair Research Laboratory, Harare, Zimbabwe. SUBJECTS: Sera and dried blood spots samples were available from 379 women from Mbare, Harare and Mupfure, Shamva District, Zimbabwe who had participated in HIV studies conducted by Blair Research Laboratory. MAIN OUTCOME MEASURES: Results of the GPA and Recombigen HIV-1/2 ELISA using serum and dried blood spots. RESULTS: With the Recombigen HIV-1/2 ELISA as the gold standard, sensitivity and specificity of the GPA were 100% and 99.2% respectively using serum. With dried blood spots sensitivity and specificity of the GPA test were 100%. The cost of analysing one sample, based on cost of reagents and accessory materials only, was Z$300 for GPA compared to Z$1,200 for ELISA. Furthermore, hands-on time was significantly reduced with the GPA compared to ELISA. CONCLUSION: The GPA method is simple, less labour intensive and much cheaper, yet is equally sensitive when compared to standard ELISA. The high sensitivity with blood spots makes the test ideal for large-scale epidemiological studies in remote rural areas with no infrastructure for advanced diagnostic methods.

How better drugs could change kala-azar control. Lessons from a cost-effectiveness analysis.

Conditional on correct diagnosis and treatment, current drug regimens for visceral leishmaniasis (VL) will only prevent about 90% of deaths. Furthermore, the cost of pentavalent antimonials, the long duration of the regimen and its parenteral administration are major obstacles for patients. Poor patient compliance and the use of counterfeit drugs contribute to therapeutic failure, amplification of the reservoir and the appearance of drug resistance. We assessed the impact of potential improvements in chemotherapy on the cost-effectiveness of VL test-treatment strategies. Competing test-treatment strategies were compared in a formal decision analysis - from the viewpoint of the clinician facing a VL suspect -, with avoided VL-mortality and cost as outcomes of interest. Sensitivity analysis was done involving the following parameters: efficacy, toxicity and cost of treatment including patient care. When safer and more efficacious drugs are considered, they only result in a more cost-effective strategy if the total cost of treatment falls below US$ 390 per patient. A serological test-treatment strategy remains the optimal choice, also when better drugs become available.

Urinary hydatid antigen detection by coagglutination, a cost-effective and rapid test for diagnosis of cystic echinococcosis in a rural or field setting.

We describe here coagglutination (Co-A), a rapid slide agglutination test for the detection of hydatid antigen in the urine for the diagnosis of cystic echinococcosis (CE). Paired urine and serum samples were collected from 16 patients with surgically confirmed CE, 10 patients with ultrasound-proven CE, 14 patients with clinically diagnosed CE, 24 patients with various parasitic diseases other than CE, and 25 healthy control subjects. Co-A detected excreted hydatid antigen in the concentrated urine of 7 of 16 (43.75%) surgically confirmed cases, 6 of 10 (60%) ultrasound-proven cases, and 8 of 14 (57.14%) clinically diagnosed cases of CE. A false-positive reaction was observed with 12.50% of control urine specimens from patients with parasitic diseases other than CE and 12% of urine samples from healthy controls. The circulating antigen was detected in the serum in 13 of 16 (81.25%) surgically confirmed cases, 6 of 10 (60%) ultrasound-proven cases, and 13 of 14 (92.86%) clinically diagnosed cases of CE. False-positive reactions were observed with three sera (12.5%) from controls with other parasitic diseases. The low sensitivity of Co-A for detection of antigen in the urine of a patient whose serum was positive for the antigen is possibly due to low levels of antigen in the urine. Unlike the collection of blood for serum, which is an invasive procedure and also requires technical expertise and disposable syringes, urine can be collected easily and frequently without causing any inconvenience to the patient. Urine as a clinical specimen alternative to serum would be immensely useful in the diagnosis of CE, particularly in a rural or field setting. In such situations as well as in poorly equipped laboratories, Co-A has the potential to be used as a simple, rapid, and economical slide agglutination test for detection of urinary hydatid antigen in the diagnosis of CE.

Cost-effectiveness of competing diagnostic-therapeutic strategies for visceral leishmaniasis.

Reported are the results of a formal decision analysis which facilitated the choice of the most appropriate test-treatment strategy for visceral leishmaniasis in areas where the disease is endemic. The following strategies were compared: treatment of all suspects (strategy A); testing by means of parasitological investigation followed by treatment of positives (strategy B); two-step testing by means of the direct agglutination test (DAT) followed by treatment of patients with high titres as well as those with parasitologically confirmed borderline titres (strategy C); and DAT followed by treatment of positives (strategy D). The results for each strategy were expressed as costs in US$ per death averted. The effectiveness of strategies C and D was close to that of strategy A and far better than that of strategy B. The cost-effectiveness ratio for strategies C and D (US$ 465 per death averted) was not substantially higher than that of testing by means of parasitological investigation followed by treatment of positives (strategy B), which was the most cost-effective strategy at US$448 per death averted. At current prices of antimonial drugs, the cost of test-treatment strategies depends more on the cost of treatment than on that of testing. The use of a sensitive serological test such as the DAT is recommended as the basis of test-treatment strategies for visceral leishmaniasis in areas where the disease is endemic.

PIP: This paper reports the results of a formal decision analysis. This facilitates in choosing the most appropriate test-treatment strategy for visceral leishmaniasis in endemic areas. Four strategies were compared based on their cost-effectiveness expressed in US dollars per death averted. These strategies include: (A) testing by means of parasitological investigation followed by treatment of positives; (B) two-step testing by means of the direct agglutination test (DAT); (C) treatment of patients with high titers as well as those with parasitologically confirmed borderline titers; and (D) DAT followed by treatment of positives. The results showed that the effectiveness of strategies C and D was close to that of strategy A and far better than that of strategy B. The cost-effectiveness ratio for strategies C and D was US$465 per death averted, which is not substantially higher than that of strategy B, while strategy B is the most cost-effective at US$448 per death averted.

The fat emulsion agglutination test: a reliable and cost effective alternative to the latex agglutination test for rapid bedside CRP measurement.

We compared two tests for bedside C reactive protein (CRP) measurement: the latex agglutination test (LAT) and the fat agglutination test (FAT). FAT is based on the property of CRP to agglutinate fat emulsions in the presence of CaCl2. The sensitivity, specificity and accuracy of FAT and LAT to detect a CRP > 10 mg/l, determined with radial immunodiffusion (n = 500 pediatric patients, CRP range 0- > 80 mg/l), were 91%, 82% and 90% respectively for FAT and 82%, 95% and 85% for LAT. FAT reagent could be stabilized with NaN3 (0.02%) for at least one year, when stored at 4 degrees C (n = 49). NaN3 (0.02%) had no effect on agglutination of FAT (n = 40). In conclusion, in pediatric patients, FAT is a reliable and cost effective alternative to LAT, if serum samples are used.

Serotyping of Streptococcus pneumoniae by agglutination assays: a cost-effective technique for developing countries.

There is a need for additional data on the distribution of pneumococcal serotypes in developing countries. We report the use of a coagglutination (COA) and a latex agglutination (LA) test for serotyping Streptococcus pneumoniae which were evaluated using 114 clinical isolates in Vellore, India. In tests to serotype 30 fresh isolates of pneumococci from meningitis (8 isolates), bacteraemia/septicaemia (21 isolates) and peritonitis (1 isolate) cases, there was complete concordance among the three methods. An additional 20 isolates (11 from cerebrospinal fluid and 9 from blood cultures) were serotyped using both LA and COA, with full agreement between the results. With a further 30 isolates, there was 93% concordance for the COA types with serotypes assigned by a WHO reference laboratory. The COA and LA serotyping results were equivalent in accuracy to those obtained using quellung serotyping. Both these agglutination tests are rapid, valid, and relatively cheap, and with appropriate validation by reference laboratories they could be more widely used in developing countries to obtain local and regional data on pneumococcal serotype distribution.

Cost-effective, clinically relevant method for rapid identification of beta-hemolytic streptococci and enterococci.

Currently popular agglutination and coagglutination methods for the identification of beta-hemolytic streptococci, although rapid and simple to perform, are costly. Furthermore, they fail to distinguish between clinically relevant species and normal flora of the same serogroup. We investigated the use of a series of four physiologic tests to differentiate beta-hemolytic streptococci and enterococci into five clinically relevant groups. We also investigated the use of a new product, Visi-Spot, and evaluated an alternate method for the detection of beta-D-glucuronidase production. Our results suggest that for most routine processing of beta-hemolytic streptococci, physiologic tests are sufficiently rapid, more accurate, and far less costly to perform than serologic methods. The facility of our scheme is enhanced by the use of the Visi-Spot test and the substitution of a commercially available product for more traditional methods of detecting beta-D-glucuronidase.