Economic and feasibility comparison of the dRIT and DFA for decentralized rabies diagnosis in resource-limited settings: The use of Nigerian dog meat markets as a case study.

BACKGROUND: Rabies lyssavirus (RABV) is the aetiologic agent of rabies, a disease that is severely underreported in Nigeria as well as elsewhere in Africa and Asia. Despite the role that rabies diagnosis plays towards elucidating the true burden of the disease, Nigeria-a country of 180 million inhabitants-has a limited number of diagnostic facilities. In this study, we sought to investigate two of the World Organization for Animal Health (OIE)-recommended diagnostic assays for rabies-viz; the direct fluorescent antibody test (DFA) and the direct rapid immunohistochemical test (dRIT) in terms of their relative suitability in resource-limited settings. Our primary considerations were (1) the financial feasibility for implementation and (2) the diagnostic efficacy. As a case study, we used suspect rabies samples from dog meat markets in Nigeria. METHODS/PRINCIPAL FINDINGS: By developing a simple simulation framework, we suggested that the assay with the lowest cost to implement and routinely use was the dRIT assay. The costs associated with the dRIT were lower in all simulated scenarios, irrespective of the number of samples tested per year. In addition to the cost analysis, the diagnostic efficacies of the two assays were evaluated. To do this, a cohort of DFA-positive and -negative samples collected from dog meat markets in Nigeria were initially diagnosed using the DFA in Nigeria and subsequently sent to South Africa for diagnostic confirmation. In South Africa, all the specimens were re-tested with the DFA, the dRIT and a quantitative real-time polymerase chain reaction (qRT-PCR). In our investigation, discrepancies were observed between the three diagnostic assays; with the incongruent results being resolved by means of confirmatory testing using the heminested reverse transcription polymerase reaction and sequencing to confirm that they were not contamination. CONCLUSIONS/SIGNIFICANCE: The data obtained from this study suggested that the dRIT was not only an effective diagnostic assay that could be used to routinely diagnose rabies, but that the assay was also the most cost-effective option among all of the OIE recommended methods. In addition, the results of our investigation confirmed that some of the dogs slaughtered in dog markets were rabies-positive and that the markets posed a potential public health threat. Lastly, our data showed that the DFA, although regarded as the gold standard test for rabies, has some limitations-particularly at low antigen levels. Based on the results reported here and the current challenges faced in Nigeria, we believe that the dRIT assay would be the most suitable laboratory test for decentralized or confirmatory rabies diagnosis in Nigeria, given its relative speed, accuracy, cost and ease of use.

Comparative cost-effectiveness of immunoassays and FLOTAC for diagnosing Giardia spp. infection in dogs.

BACKGROUND: Giardia spp. is a protozoan pathogen and is the most common enteric parasite of domestic animals and humans. Assays for detecting infection in fecal samples using direct or indirect examinations are important tools for diagnosing the disease. The objective of the present study was to compare the cost-effectiveness of immunoassays and FLOTAC technique for diagnosing Giardia spp. infection in dogs. RESULTS: Fecal samples from 80 positive stray dogs were tested for the presence of copro-antigens of Giardia spp. using the direct immunofluorescence assay (IFA), a rapid enzyme-linked immunosorbent assay (ELISA) and the FLOTAC double technique. All methods were performed in accordance with the instructions reported in the original description for each technique. The results showed that ELISA can be run in less time than IFA and almost at the same time of the FLOTAC technique. Among the tests used in this study, FLOTAC had the lowest cost per correct diagnosis, compared with immunoassays. CONCLUSIONS: The results from this cost-effectiveness analysis, in combination with the sensitivity and specificity of the FLOTAC technique, suggest that the FLOTAC technique can be use in the routine diagnosis of Giardia spp. infection in dogs.

A Survey of Oral Cancer Screening Insurance Coverage in New York City.

Clinical studies show that fewer than 25% of people who visit a dentist regularly are screened for oral cancer, and that the majority of oral cancers present at an advanced stage, when cure rates are already abysmal. This study explores the current status of oral cancer screening coverage among a variety of insurance providers in New York City. The study focuses on determining the coverage and frequency of the cluster of salient CDT (dental) codes surrounding oral cancer screenings.

Diagnostic evaluation of rapid tests for scrub typhus in the Indian population is needed.

BACKGROUND: Owing to frequent outbreaks witnessed in different parts of the country in the recent past, scrub typhus is being described as a re-emerging infectious disease in India. Differentiating scrub typhus from other endemic diseases like malaria, leptospirosis, dengue fever, typhoid, etc. is difficult due to overlapping clinical features and a lower positivity for eschars in Asian populations. Hence, the diagnosis heavily relies on laboratory tests. DISCUSSION: Costs and the need of technical expertise limit the wide use of indirect immunoperoxidase or immunofluorescence assays, ELISA and PCR. The Weil-Felix test is the most commonly used and least expensive serological test, but lacks both sensitivity and specificity. Hence, the diagnosis of scrub typhus is often delayed or overlooked. With due consideration of the cost, rapidity, single test result and simplicity of interpretation, rapid diagnostic tests have come into vogue. However, evaluation of rapid diagnostic tests for scrub typhus in the Indian population is needed to justify or discourage their use. CONCLUSION: Research studies are needed to find the most suitable test in terms of the rapidity of the result, simplicity of the procedure, ease of interpretation and cost to be used in the Indian populace.

A molecular method for typing Herpes simplex virus isolates as an alternative to immunofluorescence methods.

BACKGROUND: Typing of Herpes simplex virus (HSV) isolates is required to identify the virus isolated in culture. The methods available for this include antigen detection by immunofluorescence (IF) assays and polymerase chain reaction (PCR). This study was undertaken to standardize a molecular method for typing of HSV and compare it with a commercial IF reagent for typing. OBJECTIVES: To compare a molecular method for typing HSV isolates with a monoclonal antibody (MAb) based IF test. STUDY DESIGN: This cross-sectional study utilized four reference strains and 42 HSV isolates obtained from patients between September 1998 and September 2004. These were subjected to testing using an MAb-based IF test and a PCR that detects the polymerase ( pol ) gene of HSV isolates. RESULTS: The observed agreement of the MAb IF assay with the pol PCR was 95.7%. Fifty four point eight percent (23/42) of isolates tested by IF typing were found to be HSV-1, 40.5% (17/42) were HSV-2, and two (4.8%) were untypable using the MAb IF assay. The two untypable isolates were found to be HSV-2 using the pol PCR. In addition, the cost per PCR test for typing is estimated to be around Rs 1,300 (USD 30), whereas the cost per MAb IF test is about Rs 1,500 (USD 35) including all overheads (reagents, instruments, personnel time, and consumables). CONCLUSION: The pol PCR is a cheaper and more easily reproducible method for typing HSV isolates as compared to the IF test. It could replace the IF-based method for routine typing of HSV isolates as availability of PCR machines (thermal cyclers) is now more widespread than fluorescence microscopes in a country like India.

An improved and cost-effective methodology for the reduction of autofluorescence in direct immunofluorescence studies on formalin-fixed paraffin-embedded tissues.

Interference by autofluorescence is one of the major shortcomes of immunofluorescence analysis by confocal laser scanning microscopy (CLSM). CLSM requires minimal tissue autofluorescence and reduced unspecific fluorescence background, requisites that become more critical when direct immunofluorescence studies are concerned. To control autofluorescence, different reagents and treatments can be used. Until now, the efficacy of the processes described depended on the tissue type and on the processing technique, no general recipe for the control of autofluorescence being available. Using paraffin sections of archival formalin-fixed murine liver, kidney and pancreas, we have found that previously described techniques were not able to reduce autofluorescence to levels that allowed direct immunofluorescence labelling. In this work, we aimed at improving currently described methodologies so that they would allow reduction of the autofluorescent background without affecting tissue integrity or direct immunofluorescence labelling. We have found that the combination of short-duration, high-intensity UV irradiation and Sudan Black B was the best approach to reduce autofluorescence in highly vascularised, high lipofuscins' content tissues, such as murine liver and kidney, and poorly vascularised, low lipofuscins' content tissues such as the pancreas. In addition, we herein show that this methodology is highly effective in reducing autofluorescent background to levels that allow detection of specific signals by direct immunofluorescence.

Resource consumption in the infection control management of pertussis exposure among healthcare workers in pediatrics.

OBJECTIVE: To assess consumption of resources in the infection control management of healthcare workers (HCWs) exposed to pertussis and to assess avoidability of exposure. SETTING: Tertiary care children's medical center. METHODS: Analysis of the extent of and reasons for HCW exposure to pertussis during contact with children with the disease, whether exposures were avoidable (because of the failure to recognize a case or to order or adhere to isolation precautions) or unavoidable (because the case was not recognizable or because another diagnosis was confirmed), and the cost of implementing exposure management. INTERVENTIONS: Interventions consisted of an investigation of every HCW encounter with any patient who was confirmed later to have pertussis from the time of hospital admission of the patient, use of azithromycin as postexposure prophylaxis (PEP) for exposed HCWs, performance of 21-day surveillance for cough illness, testing of symptomatic exposed HCWs for Bordetella pertussis, and enhanced preexposure education of HCWs. RESULTS: From September 2003 through April 2005, pertussis was confirmed in 28 patients (median age, 62 days); 24 patients were admitted. For 11 patients, pertussis was suspected, appropriate precautions were taken, and no HCW was exposed. Inadequate precautions for 17 patients led to 355 HCW exposures. The median number of HCWs exposed per exposing patient was 9 (range, 1-86 HCWs; first quartile mean, 2; fourth quartile mean, 61). Exposure was definitely avoidable for only 61 (17%) of 355 HCWs and was probably unavoidable for 294 HCWs (83%). The cost of 20-month infection control management of HCWs exposed to pertussis was $69,770. The entire cohort of HCWs involved in direct patient care at the facility could be immunized for approximately $60,000. CONCLUSIONS: Exposure of HCWs to pertussis during contact with children who have the disease is largely unavoidable, and management of this exposure is resource intensive. Universal preexposure vaccination of HCWs is a better utilization of resources than is case-based postexposure management.

Comparison of the RSV respi-strip with direct fluorescent-antigen detection for diagnosis of respiratory syncytial virus infection in pediatric patients.

The RSV Respi-Strip was compared to the SimulFluor respiratory screen for detecting respiratory syncytial virus in nasopharyngeal aspirates from pediatric patients. Of samples tested, 115/239 (49%) were positive by direct fluorescent-antigen detection. The sensitivity and specificity of the RSV Respi-Strip were 92% (95% confidence interval [CI], 86% to 96%) and 98% (95% CI, 94% to 100%), respectively, with a diagnostic efficiency of 95%.

Methods in virus diagnosis: immunofluorescence revisited.

BACKGROUND: Immunofluorescence (IF) has been used in many laboratories for virus diagnosis but has begun to fall inappropriately out of favour as a diagnostic method as pressure on budgets and for objective quality control increases. OBJECTIVES: To review the status, value and benefits of IF. CONCLUSIONS: IF has, we believe, still a valuable role to play in routine virus diagnosis because it is rapid, accurate (with properly validated reagents), flexible and, by giving feedback on the quality of the specimens collected, promotes dialogue with the customer clinicians to their benefit and to that of the diagnostic laboratory. These benefits are not easily duplicated by other methods or techniques. While such rapid diagnosis primarily benefits the individual patient, providing results within a clinically relevant time has a secondary effect of increasing use of the service. It is our experience that the availability of rapid IF diagnosis (as opposed to culture or serology) for respiratory viral infections leads to a substantial increase in its use, thereby enhancing the amount and breadth of the resultant epidemiological data.

A comparison study of different methods used in the detection of Giardia lamblia.

OBJECTIVE: The purpose of this study was to compare results obtained using a single fecal specimen for O&P examination, direct immunofluorescent assay (DFA), and three immunodiagnostic techniques. DESIGN: Sixty-eight human fecal specimens were collected and examined by each method. The O&P and the DFA were used as the reference method. SETTING: The study was performed at the research laboratory in the Medical Technology Department at The University of Southern Mississippi. PATIENTS OR OTHER PARTICIPANTS: The fecal specimens were collected from individuals with a suspected Giardia lamblia infection. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The amount of agreement and disagreement between methods. 1. The sensitivity and specificity of each method. 2. The working time and cost per specimen for each method. RESULTS: There was complete agreement among methods on 52 specimens (21 positive, 31 negative). Eight specimens were positive by all immunologic methods, but negative by O&P. The remaining eight specimens (12%) demonstrated discrepancies among methods. Sensitivity and specificity of each assay ranged from 91% to 100% and 89% to 100%, respectively. The cost per specimen ranged from $11.62 for the DFA method to $32.54 for the O&P method. The average cost per specimen for ELISA and EIA averaged $26.86. CONCLUSION: The study supported findings of other investigators who concluded that immunologic methods have the greater sensitivity. The immunologic methods were more efficient, quicker, and economical than the conventional O&P method.

Detection of Bordetella pertussis in a clinical laboratory by culture, polymerase chain reaction, and direct fluorescent antibody staining; accuracy, and cost.

Control of Bordetella pertussis in the community is hampered by slow and insensitive diagnostic tests. We therefore examined the accuracy and cost of culture, direct fluorescent antibody (DFA) staining, and PCR in a routine clinical laboratory. Six hundred thirty seven nasopharyngeal swabs and aspirates in casamino acids transport medium were cultured, stained with polyclonal (Difco), and monoclonal (BL-5 and Accu-Mab) anti-B. pertussis reagents, and amplified by an IS481-specific PCR. PCR products were detected by a hybridization-enzyme immunoassay kit (Gen-eti-k DEIA, DiaSorin), with confirmation by a second PCR in a separate laboratory. Sensitivities and specificities of culture, polyclonal DFA, monoclonal DFA, and PCR were 36 and 100%, 11.4 and 94.6%, 8.3 and 98. 4%, and 95.0 and 99.3%, respectively, with a prevalence of 15.7%. The DFA tests were the most economical, and the PCR cost was 31% higher than culture. This study suggests that with minor improvements in economy, pertussis PCR can be implemented in a clinical laboratory with marked improvement in diagnostic accuracy.

Chickenpox outbreak among the staff of a large, urban adult hospital: costs of monitoring and control.

Chickenpox is a highly infectious disease of childhood, but there are increasing reports of occurrence in adults. A recent community epidemic of chickenpox resulted in 20 documented cases of adult chickenpox in a large metropolitan hospital. Nine of these cases resulted from direct exposure to an index patient and four were in tertiary contacts of the three index patients associated with the nosocomial outbreak. A total of 165.6 person-days of work were lost (estimated $18,000 cost) as a result of this outbreak, and 70 infection control unit person-hours were required during the investigation and control. This article reports a nosocomial epidemic and reviews guidelines for identification and control of adult chickenpox in a large hospital complex.