Exploring global and country-level barriers to an effective supply of leishmaniasis medicines and diagnostics in eastern Africa: a qualitative study

OBJECTIVES

To understand stakeholders' perceptions of the access barriers to quality-assured diagnostics and medicines for leishmaniasis in the high-burden region of eastern Africa, and to identify key bottlenecks to improve the supply of commodities for neglected tropical diseases.

DESIGN

Desk reviews and qualitative in-depth interview study with purposive sampling.

METHODS

A landscape analysis through literature and desk review was performed. Next, 29 representatives from international organisations, non-governmental agencies, national control programmes from six countries (Ethiopia, Kenya, Somalia, South Sudan, Sudan and Uganda) and manufacturers were interviewed between May and July 2018. Participants were selected purposively and expanded through a snowballing technique.Data analysis was aided by NVivo, applying the framework method as a part of the thematic content analysis approach.

RESULTS

The barriers along the visceral leishmaniasis (VL) supply chain were identified as emerging themes, grouped across supply chain activities and health systems component(s). Stakeholders expressed the perception of progress, but bottlenecks persist. VL medicines, in general, lack multisource production capacity and with small market volume, expansion of suppliers is difficult. Procurement is plagued by forecasting difficulties, complex regulatory policies and procedures, and distribution challenges. Weak communication and coordination across different levels resulted in shortages and loss of trust among different actors. Cross-cutting issues spanned from limited political and resource commitment due to low awareness and limited in-country capacity. However, study respondents were optimistic to pursue several remedies, most importantly to build bridges between supply and demand sides through continued dialogue and collaborations. Diagnostics supply has mostly been overlooked; thus, improved investment in this area is needed.

CONCLUSIONS

Addressing supply barriers in eastern Africa requires consistent, specific efforts at the global and national levels, progressing from current partnerships and agreements. Priority actions include pooled procurement, improved forecast, and increased commitment and resources. Sustainability remains an elusive goal, yet to be integrated into discussions moving forward.

Comparison of Indirect Immunofluorescence and Passive Particle Agglutination for the Detection of Mycoplasma Pneumoniae Antibodies

BACKGROUND

Mycoplasma pneumoniae (MP) is the most predominant pathogen causing pneumonia. The present study compares two serological assays, the indirect immunofluorescence assay (IFA) and the passive particle agglutination assay (PPA), in order to assist clinicians in selecting accurate diagnosis methods.

METHODS

Sera from 127 patients suffering from mycoplasma pneumonia and 76 from the healthy group were analyzed simultaneously by PPA and IFA. Receiver operating characteristic analyses were performed to evaluate the detection value of PPA and IFA for mycoplasma pneumoniae. The kappa coefficient was analyzed to evaluate the agreement between the IFA and PPA assay.

RESULTS

The AUC of PPA and IFA was more than 0.70, suggesting both assays were acceptable in clinical efficacy for detecting mycoplasma pneumoniae. When ± 1:40 antibody titers were interpreted as negative, PPA showed the highest specificity, Youden index, and AUC (86.84%, 65.58%, and 0.828, respectively), and the kappa coefficient between PPA and IFA was 0.360.

CONCLUSIONS

IFA and PPA assays have advantages and disadvantages in the detection of MP antibodies. MP anti-bodies ± 1:40 antibody titers should be interpreted as negative to improve PPA detection abilities, and the consistency of the two methods was regular agreement. Clinicians should detect MP antibodies simultaneously with two methods or analyze paired samples with one method for diagnosing whether or not MP infection is present.

[Performance of Cholera-SMART and Pathogen-Detection-Kit in the quick diagnosis of cholera]

OBJECTIVES

To compare the performance of two rapid systems for the diagnosis of cholera with the culture method, and to propose a strategy for improving the specificity and sensitivity of these systems and reducing the costs involved in making a diagnosis.

METHODS

The following institutions participated in the study: the National Bacteriology Referral Center (Centro Nacional de Referencia en Bacteriologia, CNRB) of the Costa Rican Institute for Research and Teaching in Nutrition and Health (Instituto Costarricense de Investigacion y Ensenanza en Nutricion y Salud, INCIENSA) and various hospitals in the provinces of Alajuela, Guanacaste and San Jose, in Costa Rica. A total of 237 feces samples were used to asses the performance of two tests for the rapid detection of Vibrio cholerae 01: the Pathogen Detection Kit (PDK, Intelligent Monitoring Systems, Gainesville, Florida, USA) and Cholera-SMART (New Horizons Diagnostics Corp., Columbia, Maryland, USA), both when applied directly (direct SMART and direct PDK) and when applied to specimens cultured in broth-enriched medium for 6 hours (SMART-6 and CPK-6) and for 18 hours (SMART-18 and PDK-18) at 37 degrees C in alkaline peptone water. Liquid and partially formed stools were cultured and examined by means of the rapid direct test; when the initial result was negative, the tests were repeated after culture for periods of 6 and 18 hours. Rectal and fecal swabs were obtained from feces cultured in enriched-broth medium for 6 and 18 hours. In addition, we studied the sensitivity of the rapid testing systems by using pure cultures of V. cholerae 01 (strain SOS-833, CNRB, Costa Rica) that were incubated for 18 to 24 hours, and we assessed the usefulness of observing motility under the microscope in order to rationalize the use of rapid methods.

RESULTS

The sensitivity of the direct SMART test and of the direct PDK test was 100% when samples obtained from liquid and partially formed stools and from the intestinal contents of dead bodies were used. With these samples, the direct SMART procedure showed a specificity of 100%, whereas the direct PDK procedure showed a specificity that ranged from 85.7% to 77.4%, depending on the type of sample. False positives obtained with the direct PDK method turned out to be negative with PDK-6 and PDK-18. Among the rectal and fecal swabs of persons with and without diarrhea or who had received prior treatment with antibiotics, three results that were negative with the SMART-6 procedure and two that were negative with the PDK-6 procedure turned out to be positive with the SMART-18 and PDK-18 procedures, respectively. Both systems showed excellent concordance (kappa index above 0.9) throughout. Both systems were sensitive to 6 x 10(7) colony-forming units per milliliter (cfu/mL), which was concordant with the microscopic observation of 10 microorganisms or more per field with the type of motility that characterizes vibrios (at 1000 x magnification). Samples having fewer than 10 microorganisms with the motility that characterizes vibrios had concentrations between 6 x 10(3) and 6 x 10(6) cfu/mL and became positive only after incubation in enriched-broth medium for 6 to 18 hours. We propose a strategy for diagnosing the presence of V. cholerae 01 infection in less time than it takes with traditional methods, with positive and negative predictive values of 100%.

CONCLUSIONS

The SMART and PDK systems make it possible to accurately diagnose cholera quickly, don't require sophisticated equipment or highly qualified technical personnel, and perform satisfactorily in field conditions. Through the proposed strategy, it becomes possible to improve the specificity and sensitivity of these systems and to reduce the cost of making a diagnosis, thus making them suitable for use in cholera surveillance in low-income settings where this disease is a serious public health problem.

Epidemiology of visceral leishmaniasis in Atbara River area, eastern Sudan: the outbreak of Barbar El Fugara village (1996-1997)

An outbreak of visceral leishmaniasis (VL) started in 1995 in the Atbara River area in eastern Sudan. This article reports on this outbreak and on the clinical and immunological studies that were carried out in a village, with the highest incidence of VL cases, from 1996 to 1997. A significant increase in VL incidence was recorded in a dozen villages in this area; one village, Barbar El Fugara accounted for half of the total number of cases recorded at the regional hospital. A total of 152 VL and 61 post kala-azar dermal lesion (PKDL) cases were diagnosed and treated in Barbar. Household (n = 671) and school (n = 276) surveys were performed using the leishmanin skin test (LST) and the direct agglutination test (DAT). LST positivity was 23.1 and 15.7%, whereas DAT positivity was 8.9 and 26.4% in both surveys, respectively. No gender differences were observed in either test. Unlike DAT, LST positivity was predominant in the higher age groups that also exhibited lower prevalence of VL. Few individuals were positive by both tests (1.3%, 5.2%) while the majority (68.8%, 64.8%) had no evidence of acquired immune response, suggesting either a role of innate immunity in preventing parasite establishment or, unexpectedly, lack of exposure to Leishmania. Subclinical parasitism was also demonstrated, as evidence of both acquired humoral and cellular immune responses was observed in individuals with no past history of the disease. The wide spectrum of L. donovani/human interactions may be explained by differential exposure to environmental risk factors, parasite strain polymorphisms or host genetic makeup.

The increase in occurrence of typhoid fever in Cameroon: overdiagnosis due to misuse of the Widal test?

This study investigates the cause of an apparent increase in occurrence of typhoid fever in Cameroon. The reasons explored include an overdiagnosis of the illness related to poor performance of the Widal test in laboratories and interpretation by prescribers. Questionnaires were used in 1996 to evaluate the use and interpretation of the Widal test, and checklists were used to assess its laboratory performance in 2 of the 10 provinces in Cameroon. The majority of prescribers from 20 health facilities (an average of 76% of the doctors and 61% of the nurses) could detect patients who truly had positive Widal tests and needed treatment. However, an average of 48% of the doctors and 84% of the nurses would treat patients who did not require treatment based on the Widal test result. Patients may therefore be treated unnecessarily. Most (88%) of the visited laboratories performed the Widal rapid slide agglutination test as opposed to the conventional tube agglutination test. About 14% of the laboratories that performed the rapid slide agglutination test had a score above average for each criterion evaluated. Misdiagnosis of typhoid fever leads to unnecessary expenditure and exposure of patients to the side-effects of antibiotics. In addition, misdiagnosis may result in delayed diagnosis and treatment of malaria, and other acute febrile illness.

Rapid diagnosis of cholera by coagglutination test

In this study the coagglutination test for the rapid diagnosis of cholera is evaluated in comparison with the conventional culture method. A total of 553 stool specimens were processed from cases of acute gastro-enteritis. The sensitivity and specificity of coagglutination test was 92.77% and 95.65% respectively. The coagglutination test is found to be simple, reliable and rapid method for the diagnosis of cholera.

Rapid identification of Burkholderia pseudomallei in blood cultures by a monoclonal antibody assay

Burkholderia pseudomallei is the causative agent of melioidosis. In northeast Thailand, this gram-negative bacterium is a major cause of mortality from septicemia. The definitive diagnosis of this disease is made by bacterial culture. In this study, we produced a monoclonal antibody (MAb) specific to the 30-kDa protein of B. pseudomallei by in vivo and in vitro immunization of BALB/c mice with a crude culture filtrate antigen. The MAb could directly agglutinate with all 243 clinical isolates of B. pseudomallei but not with other gram-negative bacteria, except for one strain of Burkholderia mallei. However, the MAb cross-reacted with the gram-positive Bacillus sp. and Streptococcus pyogenes. B. pseudomallei in brain heart infusion broth (BHIB) subcultured from a BacT/Alert automated blood culture system could be identified by simple agglutination with this MAb assay. The sensitivity and specificity of direct agglutination compared to the "gold standard," the culture method, were 94.12 and 98.25%, respectively. However, the MAb adsorbed to polystyrene beads or latex particles directly identified the bacterium in blood culture specimens and in BHIB subcultured from a BacT/Alert automated blood culture system. The sensitivity of the latex agglutination test was 100% for both blood culture and BHIB specimens. The specificity was 85.96 and 96.49% for the blood culture and BHIB specimens, respectively. The specificity could be increased if the nonspecific materials in the blood culture broths were eradicated by centrifugation at low speeds. Thus, a combination of blood culture and the agglutination method could be used for the rapid diagnosis of melioidosis in the routine bacteriological laboratory. This method could speed up detection of the bacterium in blood culture by at least 2 days, compared to the conventional bacterial culture method. In addition, the MAb is stable at room temperature for 2 weeks and at 4, -20, and -70 degrees C for at least 1 year. The latex reagent was stable for at least 6 months at 4 degrees C.

Mycobacterium leprae particle agglutination in diagnosis and monitoring of treatment of leprosy

IgM antibody levels against PGL-1 antigen were measured by M. leprae particle agglutination (MLPA) in 156 untreated leprosy patients. The seropositivity rate was much higher in newly untreated MB patients (84.7%) than in PB patients (19.7%). The mean MLPA titers in MB and PB declined significantly after 1 month of MDT (p < 0.001). Seropositivities in control serum specimens were 11.3 per cent in active pulmonary tuberculosis patients, 2.6 per cent in dermatologic patients and 4.4 per cent in a healthy population, in low titers. The study confirms that, anti PGL-1 assay using MLPA is a sensitive and specific diagnostic tool for the diagnosis of leprosy especially MB patients. Additionally, it provides an alternative tool in monitoring leprosy patients under MDT.

[The rapid identification of bacteria by agglutination on a slide of antibody-sensitized erythrocytes]

The method for the identification of Brucella (genus) and shigellae (species) by using slide agglutination of antibody erythrocytic immune reagents is substantiated. Such reagents, obtained from polyclonal nonadsorbed immune sera, ensure high specificity of taxon identification. The use of the proposed method may greatly accelerate bacteriological analysis.

[The development of a coagglutination reaction using staphylococcal peptidoglycan for the diagnosis of staphylococcal infection]

Our objective in this study was to develop and assess the diagnostic value of a coagglutination test with making use of peptidoglycane of Staphylococcus aureus in the identification of diseases of staphylococcal etiology. A total of 166 patients with diseases of staphylococcal etiology were examined. A test was elaborated of coagglutination with making use of peptidoglycane of Staphylococcus aureus for a differential identification of antibodies to peptidoglycan in healthy persons and patients with staphylococcosis.

Macroscopic agglutination test for rapid diagnosis of human leptospirosis

A commercially available slide agglutination test (SAT) for the diagnosis of human leptospirosis was evaluated by comparing it to an immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) and to the microscopic agglutination test (MAT). For all 108 patients, leptospirosis was diagnosed on the basis of a fourfold or greater increase in titer by MAT (seroconversion), and all but 1 of 245 controls were MAT negative (titers, <1:100). Both SAT and the IgM ELISA failed to detect one case of infection (sensitivity, 99%). Only 3 of 145 blood donors and none of the 100 patients with other illnesses were SAT positive (specificity, 99%). The overall results were similar for the three tests; however, SAT and ELISA were statistically more sensitive as initial screening tests. For 22% of the patients, the diagnosis of leptospirosis was made earlier by SAT than by MAT. SAT detected 27 (44%) of 62 MAT-negative patients with the first serum sample. ELISA and SAT had very similar results. Follow-up of patients for 1 year after the onset of symptoms showed a decreasing rate of positivity by SAT from the third month on. The rate of positivity by ELISA decreased more slowly, to about 67% by the end of the study. By MAT all patients were persistently reactive. SAT and ELISA seem to be convenient methods for the rapid and early screening for leptospirosis and could replace the less sensitive MAT. ELISA gives less subjective results than SAT and provides information on IgM kinetics, but it can be performed only by the more sophisticated laboratories. SAT is inexpensive, can be performed more quickly and more easily than ELISA, and could be used by the less well equipped laboratories.

A modified agglutination test for Neospora caninum: development, optimization, and comparison to the indirect fluorescent-antibody test and enzyme-linked immunosorbent assay

Current serologic tests used to detect antibodies to Neospora caninum require species-specific secondary antibodies, limiting the number of species that can be tested. In order to examine a wide variety of animal species that may be infected with N. caninum, a modified direct agglutination test (N-MAT) similar to the Toxoplasma gondii modified direct agglutination test (T-MAT) was developed. This test measures the direct agglutination of parasites by N. caninum-specific antibodies in serum, thus eliminating the need for secondary host-specific anti-isotype sera. The N-MAT was compared to the indirect fluorescent-antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA) with a "gold standard" serum panel from species for which secondary antibodies were available (n = 547). All positive samples tested were from animals with histologically confirmed infections. Up to 16 different species were tested. The N-MAT gave a higher sensitivity (100%) and specificity (97%) than the ELISA (74 and 94%, respectively) and had a higher sensitivity but a lower specificity than the IFAT (98 and 99%, respectively). The reduced specificity of the N-MAT was due to false-positive reactions in testing fetal fluids with particulate matter or severely hemolyzed serum. Overall, the N-MAT proved to be highly sensitive and specific for both naturally and experimentally infected animals, highly reproducible between and within readers, easy to use on large sample sizes without requiring special equipment, and useful in testing serum from any species without modification.

Antisperm antibody detection: 2. Clinical, biological, and statistical correlation between methods

PROBLEM

In clinical andrology, the detection of antisperm antibodies (ASA) is regarded as one of the most important steps in the study of male infertility. This practice is generally accepted even though there is still some disagreement about the true meaning of antisperm immunity, and there remains a good deal of controversy about the test regarded as the most suitable for the detection of antibodies directed against sperm antigens. International Workshops have tried to standardize universally accepted protocols. A panel of three or four methods is generally advised to provide a correct and complete screening of patients with antisperm immunity. The aim of the present paper is to report our studies on the correlation between direct methods (IBT, MAR test) and indirect methods (gelatin agglutination test [GAT], and tray agglutination test [TAT]) and to establish whether biological models can explain the antibody test results. An attempt was also made to establish a "predictive threshold" to explain even apparently discordant direct and indirect results.

Value of detecting immunoglobulin E antibodies for the serological diagnosis of Toxoplasma gondii infection

The presence of immunoglobulin E (IgE) antibodies was determined by using the immunosorbent-agglutination assay (ISAGA) with 611 serum samples from patients with different clinical conditions to evaluate its value for the serodiagnosis of acute Toxoplasma gondii infection. By analyzing 43 consecutively drawn serum samples from 10 pregnant women who seroconverted, we could show that specific IgE antibodies seem to appear early after infection and are usually present for less than 3 to 5 months. Therefore, we assumed that IgE antibodies seem to be detectable only during the acute or reactivated stage of infection. According to our studies, the IgE ISAGA has an overall sensitivity of only 79.5%, but a specificity of 98.0%, with positive and negative predictive values of 95.5 and 89.8%, respectively. Detection of IgE antibodies in immunosuppressed patients with reactivation of latent T. gondii infection correlates with disease activity. Despite these encouraging results, one must note that IgE antibodies were not detectable in 4 of 14 patients with very recent infection proven by seroconversion. Therefore, detection of IgE antibodies seems to correlate with early acute or reactivated toxoplasmosis, whereas negative IgE results do not exclude the possibility of the acute stage of toxoplasmosis.

Rapid method for detection of Coxiella burnetii antibodies using high-density particle agglutination

A high-density particle agglutination test, using erythrocyte-sensitizing substance from phase II Coxiella burnetii adsorbed to high-density composite particles, was developed for rapid serodiagnosis of Q fever. The test was compared with the microimmunofluorescence test for sensitivity and specificity by using 3,036 human serum samples collected in Gifu Prefecture, Japan. An excellent agreement was found between the two tests for the acute-phase group and paired serum samples, but some discordant results were observed in the single-sample group. The sensitivity and specificity of the high-density particle agglutination test were both 100% in the former group and 81.6 and 99.9%, respectively, in the latter group. The test is a very promising tool for routine serodiagnosis of Q fever because of its simplicity, sensitivity, and specificity.

Coagglutination test for serotyping Pasteurella haemolytica

A coagglutination test was described for simple, fast, and reliable detection of Pasteurella haemolytica type-specific antigens in lung lesions even in the absence of viable P. haemolytica. The coagglutinating reagents were prepared by coating protein A-producing Staphylococcus aureus cells with hyperimmune sera raised against P. haemolytica type strains. Bacterial suspensions, saline extracts, and boiled saline extracts of the bacteria were used as antigens. Homologous reactions with all types of antigens were precise. Some cross-reactions were similar to those obtained by the indirect hemagglutination test, and some additional one-way cross-reactions were identified. The coagglutination test was used for serotyping 65 P. haemolytica field strains and for the detection of P. haemolytica type-specific antigens in the lung specimens of 62 calves and 78 sheep. Ninety-four percent of the field strains could be serotyped by the coagglutination test. P. haemolytica type-specific antigens were detected in the lung specimens of 3 calves and 5 sheep that had succumbed to naturally occurring P. haemolytica pneumonia and in the lungs of 20 calves experimentally infected with P. haemolytica A1. The coagglutination test detected type-specific antigens in 36% of the lung specimens of slaughtered field sheep but not in the lungs of slaughtered field cattle with small chronic lung lesions. No reaction occurred in the case of nonpneumonic calves and sheep or when pneumonic lesions were caused by other bacteria. No P. haemolytica strains could be isolated from lung samples that were coagglutination test negative. This test is recommended as an additional method for fast and reliable serotyping of P. haemolytica.

[The outlook for improving the immunoglobulin preparations for the detection and identification of the causative agents of glanders and melioidosis]

The paper summarizes the data concerning the production and study of monoclonal antibodies (MAb) to the diagnostically significant glanders and melioidosis bacillus antigens. It evaluates the efficiency of using MAb in the gel immunodiffusion and agglutination tests as a basis of new-generation preparations for fluorescent antibody assay, indirect hemagglutination test which are used while detecting and identifying pathogenic pseudomonads. The paper defines the quality indices for monoclonal luminescent immunoglobulins and provides evidence for the benefits of monoclonal diagnostic agents over polyclonal analogues.

Evaluation of cleaving agents other than trypsin in direct agglutination test for further improving diagnosis of visceral leishmaniasis

Trypsin treatment of Leishmania promastigote antigen has proved to be indispensible in the direct agglutination test (DAT) for the diagnosis of visceral leishmaniasis (VL) and canine visceral leishmaniasis (CVL). In the present study four antigen batches were prepared with pronase (400 micrograms/ml), lipase (0.45% [wt/vol]), pancreatin (0.3% [wt/vol]), or 2-mercaptoethanol (2-ME) (1.2% [vol/vol]) at a ratio of 20:1 versus promastigote packed cell volume or a density of 10(8)/ml. Batches prepared in this way performed satisfactorily when compared with the performance of the initial trypsinated antigen. Even higher was the sensitivity and specificity of the 2-ME-processed antigen, scoring a minimum DAT titer of 1:102,400 in the VL and CVL group and a maximum of 1:400 in the negative control group. Corresponding titers ranging from 1:6,400 to 1:12,800 and 1:800 to 1:1,600 were obtained with the antigen variants processed with pronase, lipase, pancreatin, or trypsin. By combining the use of indigenous Leishmania donovani subspecies from Sudan, Bangladesh, or Morocco and incorporating 2-ME instead of trypsin in the antigen processing step, a threefold increase in titer was attained in sera from the respective areas where VL is endemic. 2-ME-processed antigen suspensions maintained stability at 4 degrees C for up to 9 months, as evidenced by the absence of autoagglutination and the reproducibility of DAT readings with standard sera. The specificity of DAT was further improved by supplementation of the sample diluent with 0.03 M urea and incubation of the test plates at 37 degrees C for 1 h. Titers ranging from 1:200 to 1:12,800 in the sera of patients and laboratory animals infected with various trypanosoma species were significantly reduce (</=1:200) or were rendered negative dilution of 1:25. Regardless of the infections caused by trypanosoma species, the sensitivity, specificity, and predictive value of a positive or negative test in DAT were 100%. Sera from patients who formerly had VL and who had been treated 6 to 36 months earlier remained reactive (>/=1:51,200) against 2-ME-processed antigen, despite the incorporation of urea into the DAT.

Evaluation of commercial antisera for Shigella serogrouping

Shigella serogrouping antisera from six companies (Becton Dickinson, Denka, Difco, Murex, Roach, and Sanofi-Pasteur) intended for the slide agglutination test and those of the Wellcolex Colour Shigella latex agglutination test were evaluated to identify quality products for Shigella identification. Forty-six reference Shigella strains (one for each serotype and species), 50 clinical strains (21 S. flexneri, 21 S. sonnei, 4 S. dysenteriae, 4 S. boydii) representing the most prevalent species and serotypes encountered in Quebec, and 9 non-Shigella strains were tested according to the manufacturers' instructions. A 3+ reaction (> or = 75% agglutination) was considered positive for the slide agglutination tests. Sensitivity varied from 47% (Roach) to 94% (Difco). For the 105 strains tested, accuracy ranged from 53% (Roach) to 91% (Wellcolex). Specificity varied from 97 to 100% for group A antisera, from 96 to 100% for group B antisera, from 88 to 100% for group C antisera, and from 95 to 99% for group D antisera. The costs of reagents required to test one strain varied from $3.50 to $13.20 (in Canadian dollars). In conclusion, Roach reagents proved to be unsatisfactory for Shigella serogrouping. Among those from the remaining companies, the Denka, Difco, and Wellcolex reagents met a performance standard of 90% accuracy.

[The diagnostic evaluation of rapid sputum technics for Pneumococcus in community-acquired pneumonia. The usefulness of Bayes theorem for clinical application]

This study aimed to quantify the diagnostic value of immunological techniques and methods for rapid analysis of sputum for pneumococcus, using sensitivity and specificity values reported in the literature to calculate positive and negative predictive values (PPV and NPV) according to Bayes formulas. Diagnostic gains of the test are calculated and compared to pretext probability. We located articles reporting sensitivity and specificity of counterimmunoelectrophoresis (CIE), coagglutination (CoA) and latex agglutination (LA) tests. We also calculated the probability ratios for the three tests. LA achieved the best overall diagnostic utility rating. CoA had the highest PPV, whereas LA offered the highest NPV. CIE was the least useful. These three tests are more useful at intermediate levels of prevalence of pneumococcus, which coincide with estimate in our population. We conclude that LA and CoA are of greater diagnostic utility for community acquired pneumonia, as they are useful for determining prevalence as well as for deciding initial antibiotic treatment.

Comparative evaluation of microagglutination test and serum agglutination test as supplementary diagnostic methods for brucellosis

The diagnosis of brucellosis in cattle and small ruminants requires the use of more than one serological test. The complement fixation test (CFT), the rose bengal test (RBT), and the serum agglutination test (SAT) are among the most useful tests for routine diagnosis. The microagglutination test (MAT) was developed as a simpler and more efficient test than the SAT. The relative efficacy of this test compared with that of the SAT was evaluated by using brucella-free sheep and goats prior to and after vaccination treatment. The specificities of the MAT and the SAT were 100%. Of the ewes and goats with a vaccination history, one ewe, expectedly a negative responder, had reactions in the MAT, the complement fixation test, and the rose bengal test but not in the SAT, suggesting a lower sensitivity of the SAT in this case. The calculated sensitivities of the MAT and the SAT were 93.9%. The agreement between MAT and SAT results from nonresponders was examined by using sera from unvaccinated lambs and kids (95.2% agreement), unvaccinated ewes and goats (84.4%), and ewes and goats with a vaccination history (43.9%). For the latter group higher levels of agglutination units were observed by the MAT than by the SAT in 51.5% of the samples. In testing sera from positive reactors after vaccination neither method was superior (MAT values were greater than SAT values for 23.5% of the samples, and MAT values were less than SAT values for 21.9% of the samples). Comparison of the methods on the individual sample level revealed a significant correlation between the MAT and the SAT (r = 0.96 +/- 0.005; P < 0.001). Since the MAT is simpler to perform than the SAT and can potentially be automated, the inclusion of the MAT as a supplementary test in brucellosis control programs is recommended.

Leish-KIT, a stable direct agglutination test based on freeze-dried antigen for serodiagnosis of visceral leishmaniasis

In order to increase the application potential of the direct agglutination test (DAT) for the detection of anti-Leishmania antibodies in human serum samples, we developed an antigen based on stained and freeze-dried Leishmania donovani promastigotes. We describe here the evaluation of the performance of the DAT based on this freeze-dried antigen. It was shown that the freeze-dried antigen remains fully active, even after storage at 56 degrees C for 18 months. With a cutoff value of 1:1,600, the sensitivity of the DAT was shown to be 92% and the specificity of the test was 99.7%, which were comparable with the results found for the DAT based on liquid antigen. The major advantages of the freeze-dried antigen are that the production of a large batch of this antigen allows reproducible results in the DAT over a long period of time and that the freeze-dried antigen can be stored at ambient temperature, which, as was shown, makes the test a valuable diagnostic tool for use in the field.

Comparison of two rapid commercial tests with complement fixation for serologic diagnosis of Mycoplasma pneumoniae infections

The complement fixation (CF) test is the current reference serologic test for the diagnosis of Mycoplasma pneumoniae infection. However, it is reported to be insensitive and nonspecific, and it is labor intensive. To determine if a faster and more sensitive diagnosis of M. pneumoniae could be obtained, we examined 50 paired serum samples from patients with suspected M. pneumoniae infection by the CF test and two commercial rapid antibody detection kits, the Remel M. pneumoniae immunoglobulin G (IgG)-IgM antibody test system (Remel, Lenexa, Kans.) and the Seradyn Color Vue M. pneumoniae IgG-IgM kit (Seradyn, Indianapolis, Ind.). The Remel test, a 5-min qualitative immunobinding assay, detected antibodies in three patient serum samples with CF titers of 32 and in all but one sample with titers of > or = 64. The Seradyn test, a 40-min qualitative agglutination test, was less sensitive than CF or Remel. The Seradyn test was positive in 68% of cases, compared with 94 and 96% of cases tested by CF or Remel, respectively. Both commercial tests are faster and less technically demanding to perform than is the CF test.

Evaluation of new agglutination test for identification of oxacillin-susceptible and oxacillin-resistant Staphylococcus aureus

A new agglutination test (Monostaph +; Bionor, Skien, Norway) has been developed. This new agglutination test has been compared with two other agglutination tests for the identification of 128 isolates of Staphylococcus aureus and 82 coagulase-negative staphylococci. The sensitivities of both Monostaph + and Pastorex Staph-Plus were excellent (98.7 and 97.4%, respectively) in detection of oxacillin-resistant Staphylococcus aureus. The specificity was 96.4% (two Staphylococcus epidermidis isolates and one Staphylococcus hominis isolate were false positive).

Comparison of GonoGen, GonoGen II, and MicroTrak direct fluorescent-antibody test with carbohydrate fermentation for confirmation of culture isolates of Neisseria gonorrhoeae

When testing 248 clinical isolates of Neisseria gonorrhoeae, the sensitivity was 100% with GonoGen (Becton Dickinson Microbiology Systems), 99.6% (247 of 248) with GonoGen II (Becton Dickinson), 97.2% (241 of 248) with the MicroTrak direct fluorescent-antibody test (Syva), and 97.6% (242 of 248) with Rapid Fermentation Agar carbohydrates (Remel). Of 62 isolates of other Neisseria species, none was misidentified as N. gonorrhoeae by GonoGen, MicroTrak, or Rapid Fermentation Agar carbohydrates but 7 (31.8%) of 22 isolates of N. meningitidis gave strong, repeatedly false-positive results with GonoGen II. The sensitivity of all four assays was good to excellent, but all positive GonoGen II results should be confirmed with an independent assay, especially when isolates are recovered from sites where N. meningitidis is likely. Positive results from any of the assays should be routinely confirmed when dictated by specific clinical, legal, or microbiological circumstances.

Evaluation of an agglutination HIV-1 + 2 antibody assay

Studies have shown that an HIV (HIV-PA) agglutination assay (Serodia) for the detection of antibody to human immunodeficiency virus (HIV) can be as sensitive and as specific as enzyme-linked immunosorbent assay (ELISA). However, since this HIV assay was designed to detect antibody to the HIV-1 virus, a substantial number of HIV-2 positive sera are missed by this assay. Since the HIV-2 has now been found throughout the world this test is becoming less suitable. The new HIV-1 + 2 assay version (HIV-1 + 2 PA) was evaluated in 300 sera, which contained 50 HIV-1, 40 HIV-2 and 10 HIV-1/HIV-2 antibody positive samples, and a sensitivity and specificity of 100% and 99%, respectively, was obtained. Whereas all HIV-2 positive sera were detected by the new HIV-1 + 2 version, 26% (13/50) were missed by the old version of the agglutination test. It is concluded that the HIV-1 + 2 PA assay is a promising instrument free assay which can be used for screening purposes in areas where both HIV-1 and HIV-2 are present.

Sensitivity of HIV-antibody assays determined by seroconversion panels

OBJECTIVES

To determine the sensitivity of HIV-antibody assays for detecting low levels of HIV antibody using seroconversion and other panels containing plasma of varying titres.

METHODS

Eight HIV-antibody assays, available under the World Health Organization bulk-procurement agreement, were evaluated on sets of sequential plasma samples derived from 11 individuals who had recently become HIV-infected (seroconversion panels). In addition, two non-seroconversion panels, consisting of low performance (titre) and mixed titre samples were used to further define the sensitivity of the assays. The eight assays included two rapid tests, one simple test, and five enzyme-linked immunosorbent assays (ELISA).

RESULTS

On average, the eight assays detected antibody 0.5-4.8 days later than the reference test (Abbott HIV-1/HIV-2 3rd generation ELISA); these differences were statistically significant for six of the eight tests. All tests performed well on the low performance and mixed titre panels. All eight assays also had comparable sensitivity to that of the reference test on a large panel of known positive plasma. The additional risk of missing an infectious unit of blood during seroconversion by using the least sensitive rather than the reference test was estimated to be 1 in 7600 and 1 in 76 million at annual HIV incidence rates of 1 and 0.0001%, respectively. The cost of eliminating this additional risk by using the reference test is between US$ 15,150 and 151 million per unit detected at the above incidence rates.

CONCLUSIONS

Although there are differences in sensitivity between the assays when used to test blood from individuals during the course of seroconversion, the differences are small, and all eight tests are appropriate for use as screening tests.

Rapid detection of Vibrio cholerae O1 in stools of Peruvian cholera patients by using monoclonal immunodiagnostic kits. Loyaza Cholera Working Group in Peru

We compared stool culture with two commercial Vibrio cholerae O1 rapid diagnostic kits which detect antigen in 100 adults with cholera in Peru. Serum vibriocidal-antibody titer was used as an external reference. Both rapid diagnostic kits appeared to detect cholera more frequently than did culture and were highly specific.

Comparative assessment of the leprosy antibody absorption test, Mycobacterium leprae extract enzyme-linked immunosorbent assay, and gelatin particle agglutination test for serodiagnosis of lepromatous leprosy

A comparative assessment of three serological methods for leprosy diagnosis (the fluorescent leprosy antibody absorption [FLA-ABS] test, the Mycobacterium leprae soluble-extract enzyme-linked immunosorbent assay [ELISA], and the M. leprae particle agglutination [MLPA] test) was carried out. The objective was to identify their performance in clinical and epidemiological diagnosis of leprosy. The study group included 45 lepromatous leprosy patients under treatment. Specificity was > 95% for all three assays, and sensitivity was 95, 58, and 74% for the FLA-ABS test, the MLPA test, and the ELISA, respectively. The only cross-reactivity for M. tuberculosis-infected patients was with the soluble-extract ELISA. Although the FLA-ABS test displayed the highest specificity and sensitivity values, it can only be used in well-developed laboratories, and the patient's clinical and epidemiological background must be considered when results are interpreted because the test remains positive after therapeutic success and could be positive for some household contacts. The MLPA test is easier to perform and interpret, and it is adequate for small laboratories and epidemiological studies intended to detect active untreated or irregularly treated leprosy cases. Therefore, the FLA-ABS and MLPA tests are complementary, and both should be used for serodiagnosis of leprosy.

Evaluation of particle agglutination test for detection of HIV-I antibodies

A commercially available particle agglutination test (PA) was evaluated for its specificity and sensitivity as compared to ELISA currently used in our laboratory to detect HIV-I antibodies. A total of 463 sera from blood donors and clinical referrals were screened by PA, 45 were found to be positive (9.7%). Out of 463, 258 sera were simultaneously screened by ELISA; 28 were found to be positive (10.8%). Twelve samples showing positive results by both ELISA & PA were tested by Western blot and were confirmed to be positive. We found sensitivity of PA as compared to ELISA as 100% and specificity to be 88.44%. Readings of PA taken at 2 hrs should be reconfirmed at 24 hrs as it eliminates a number of false positives. Overall, we feel PA is fairly comparable with ELISA. It can be used in the set up where equipment and trained personnel for ELISA are not available for primary screening purposes.

Novel coagglutination method for serotyping group B streptococci

A group G streptococcal strain was coated with antibody against six different serotypes (Ia, Ib, II, III, IV, and V) of group B streptococci. The coagglutination patterns of 114 strains of group B streptococci were compared with the serotypes determined after immunoprecipitation. The specificity of the method was 100% and the sensitivity 97%. It was used for the typing of 89 invasive and 101 colonizing isolates. The new method is swift, specific, and highly sensitive. It consumes only minute amounts of antibody.