Laboratory Evaluation of a Smartphone-Based Electronic Reader of Rapid Dual Point-of-Care Tests for Antibodies to Human Immunodeficiency Virus and Treponema pallidum Infections.

BACKGROUND: Dual point-of-care tests for antibodies to human immunodeficiency virus (HIV) and Treponema pallidum allow for same-day testing and treatment and have been demonstrated to be cost-effective in preventing the adverse outcomes of HIV infection and syphilis. By recording and transmitting data as they are collected, electronic readers address challenges related to the decentralization of point-of-care testing. METHODS: We evaluated a smartphone-based electronic reader using 201 sera tested with 2 dual rapid tests for detection of antibodies to HIV and T. pallidum in Los Angeles, USA, and Lima, Peru. Tests were read both visually and with the electronic reader. Enzyme immunoassay followed by Western blot and T. pallidum particle agglutination were the reference tests for HIV and T. pallidum, respectively. RESULTS: The sensitivities of the 2 rapid tests for detection of HIV were 94.1% and 97.0% for electronic readings. Both tests had a specificity of 100% for detection of HIV by electronic reading. The sensitivities of the 2 rapid tests for detection of T. pallidum were 86.5% and 92.4% for electronic readings. The specificities for detection of T. pallidum were 99.1% and 99.0% by electronic reading. There were no significant differences between the accuracies of visual and electronic readings, and the performance did not differ between the 2 study sites. CONCLUSIONS: Our results show the electronic reader to be a promising option for increasing the use of point-of-care testing programs.

Optimal strategies for the diagnosis of community-onset diarrhea in solid organ transplant recipients: Less is more.

BACKGROUND: Diarrhea, a common complication after solid organ transplant (SOT), is associated with allograft failure and death. No evidence-based guidelines exist for the evaluation of diarrhea in SOT recipients. We performed a cost analysis to derive a testing algorithm for the diagnosis of community-onset diarrhea that minimizes costs without compromising diagnostic yields. DESIGN: A cost analysis was performed on a retrospective cohort of 422 SOT admissions for community-onset diarrhea over an 18-month period. A stepwise testing model was applied on a population level to assess test costs relative to diagnostic yields. RESULTS: Over an 18-month period, 1564 diagnostic tests were performed and 127 (8.1%) returned positive. Diagnostic testing accounted for $95 625 of hospital costs. The tests with the lowest cost per decrease in the false-omission rate (FOR) were stool Clostridium difficile polymerase chain reaction (PCR) ($156), serum cytomegalovirus quantitative PCR ($1529), stool norovirus (NV) PCR ($4673), and stool culture ($6804). A time-to-event analysis found no significant difference in the length of hospital stay between patients with and without NV testing (P=.520). CONCLUSIONS: A stepwise testing strategy can reduce costs without compromising diagnostic yields. In the first-stage testing, we recommend assessment for C. difficile, cytomegalovirus, and food-borne bacterial pathogens. For persistent diarrheal episodes, second-stage evaluation should include stool NV PCR, Giardia/Cryptosporidium enzyme immunoassay, stool ova and parasite, reductions in immunosuppressive therapy, and possibly endoscopy. Although NV testing had a relatively low cost per FOR, we recommend NV testing during second-stage evaluation, as an NV diagnosis may not lead to changes in clinical management or further reductions in length of hospital stay.

Clinical and economic impact of the introduction of a nucleic acid amplification assay for Clostridium difficile.

BACKGROUND: The clinical outcomes and cost implications of a diagnostic shift from an EIA- to PCR-based assay for Clostridium difficile infection (CDI) have not been completely described in the literature. METHODS: The impact of the PCR-based assay on the incidence and duration of CDI therapy was compared to the EIA assay for patients with a negative CDI diagnostic result. Secondary clinical and economic outcomes were also evaluated. Independent predictors of receipt of antibiotic therapy were assessed via logistic regression. RESULTS: 141 EIA and 140 PCR patients were included. Significantly more patients were started or continued on anti-CDI antibiotic therapy after a known negative assay result in the EIA group (26 patients vs. 8 patients, P = 0.002). Duration of antibiotic therapy after a known negative result was significantly shorter in the PCR group (1 vs. 4 days, P = 0.029) and a 23% reduction in the number of tests obtained per patient was observed (1.41 ± 0.86 vs. 1.82 ± 1.35, P = 0.007). The over fourfold difference in per-test cost of the EIA assay ($8.33 vs. $42.86, P < 0.0001) was offset by the overall medication costs required for the increased treatment in the EIA group ($546.60 vs. $188.96, P = 0.191). Utilization of the EIA-based CDI assay was associated with increased odds of CDI treatment after a negative test (aOR 4.71, 95% CI 1.93-11.46, P = 0.001). CONCLUSION: The transition from an EIA to PCR-based assay for diagnosing CDI resulted in a significant decrease in the number of patients treated and the duration of treatment in response to a negative test result. This significant decrease in treatment resulted in decreased costs offsetting the utilization of a more expensive molecular test for patients with a negative CDI diagnostic result.

[Selection of Laboratory Procedures to Detect Toxigenic by the 2-Step Method].

The 2-step method is an algorithm to detect toxigenic Clostridium difficile. We herein compared the sensitivities and specificities of an enzyme immunoassay (toxin A/B-EIA), toxigenic culture (TC-EIA), Loop-Mediated Isothermal Amplification assay (LAMP), and Xpert C. difficile (Xpert) with the detection of the toxin B gene by a polymerase chain reaction (PCR). The results obtained showed that the sensitivities and specificities of toxin A/B-EIA, Xpert, TC-EIA, and LAMP were 30 and 100%, 87.2 and 100%, 97.5 and 89.7%, and 95 and 100%, respectively. We also evaluated the turnaround time (TAT) and cost of toxigenic C. difficile detection. Our hospital TAT for toxin A/B-EIA and TC-EIA are 37 min and 5 days, respectively. We estimated the TAT of Xpert, LAMP, and PCR to be 105 min, 5 days, and 6 days, respectively. On the other hand, the cost to detect toxigenic C. difficile increased in the order of TC-EIA, LAMP, Xpert, and PCR. We have never experienced outbreak of Clostridium difficile infection (CDI) in our hospital, and there is less the number of CDI than other place. So we selected TC-EIA that is good sensitivity and low cost per specimen. Hereafter it'll be necessary to solve a problem it takes time, because we have to respond to outbreak of CDI quickly if it happens.

Development and validation of assay protocols for use with dried blood spot samples.

Dried blood spots (DBS)--drops of capillary whole blood collected from finger stick--represent a minimally invasive alternative to venipuncture that facilitates the collection of blood samples from research participants in naturalistic, field-based research settings. But the number of validated assays for quantifying biomarkers in DBS samples is relatively low in comparison with serum or plasma. The objective of this review is to discuss the advantages and disadvantages of DBS sampling, and to outline the steps involved in developing and validating an immunoassay for application to DBS samples. These steps include deciding on reagents, preparing calibration and quality control material, evaluating elution protocols, optimizing sample quantity, and assessing multiple aspects of assay performance, including intra- and interassay variation, lower limit of detection, accuracy, stability, and agreement between results from matched DBS and plasma samples. The broader goal of this "how-to" approach is to encourage investigators to validate, implement, and disseminate assay protocols for DBS samples in order to advance field-based research on human biology.

Nonutility of routine testing of stool for ova and parasites in a tertiary care Canadian centre.

BACKGROUND: In many clinical situations, stool examinations for ova and parasites (O&P) are routine in the work-up of patients with acute or chronic diarrhea. Frequently, these tests are found to be negative for pathogens. The purpose of this study was to examine the diagnostic yield of routine stool testing for O&P in a Canadian tertiary care centre and to estimate the potential clinical benefit of a positive result. PATIENTS AND METHODS: All stool samples sent to the central microbiology laboratory at London Health Sciences Centre were reviewed over a 5-year period ending January 2010. Initial screening was done by direct antigen testing using an enzyme immunoassay (EIA) technique followed by direct microscopy for negative results where there was a high index of suspicion and for positive results to rule out any concurrent parasites not included in the EIA kit. Pathogens identified were categorized and their potential susceptibility to metronidazole was estimated. No clinical data were available, as this was purely a utilization study. RESULTS: A total of 5812 stool tests were ordered. Of these, 5681 (97.7%) were completed. The most common reasons for an incomplete test were sample leakage (n = 38) and use of the incorrect collection kit (n = 32). Direct microscopy identified white blood cells in 17% of patients with positive testing. The most common pathogen was Giardia lamblia , which was detected in 45/83 (54%) of positive specimens. Entamoeba histolytica/Entamoeba dispar was identified in 16/83 (19%) and Cryptosporidium spp. in 10/83 (12%) of positive specimens. Microorganisms not thought to be pathogenic were identified in 7/83 (8%). Direct laboratory costs independent of labor were estimated at $1836 per clinically significant organism identified. Of the 77 specimens positive for pathogenic organisms, 62 (81%) were likely to be sensitive to treatment with metronidazole. CONCLUSION: In a tertiary care centre, the diagnostic yield of routine testing of stool for O&P during the evaluation of patients with acute or chronic diarrhea is low. Most clinically significant positive results should be responsive to metronidazole, but empirical treatment is not encouraged. Strategies to identify patients with a higher likelihood of harboring pathogenic parasites and consideration of empiric metronidazole therapy for patients at highest risk merit further research.

The significance of repeat testing in Turkish blood donors screened with HBV, HCV and HIV immunoassays and the importance of S/CO ratios in the interpretation of HCV/HIV screening test results and as a determinant for further confirmatory testing.

The purpose of this study was to investigate the intra-assay correlations amongst initial reactive and repeat screening results used in enzyme immunoassays (EIAs) for hepatitis B virus (HBV), hepatitis C virus (HCV) and HIV in blood donors. This study evaluated the value of using the power of the signal to cut-off (S/CO) ratio index for confirming anti-HCV/HIV reactive screening results, thereby touching upon the utility of S/CO indices in determining whether further confirmatory testing was necessary. Screening test results of the 72,695 blood donors were evaluated over a 1-year period. Correlation analysis among each initial test and retests was done by Pearson r test. Appropriate S/CO values to determine the need of the confirmation testing was investigated by ROC analyses. EIA intra-assay correlations were of statistical significance and were determined as follows: 0.948 for anti-HCV, 0.827 for anti-HIV and 0.948 for HBsAg. The threshold S/CO ratio values which predicted more than 95% of the confirmation test result were 3.8 for HCV and 5.6 for HIV. We were able to demonstrate a strong level of intra-assay correlation amongst EIAs, thereby eliminating the need for repetition of the screening test. Hence, we suggest that repeat screening should only be limited to HBV and HIV tests with low EIA S/CO ratios. Thus, using the power of the S/CO ratio in determining the need for HCV confirmation testing can be a cost-effective measure, especially if the S/CO value is >or=3.8.

MCE enzyme immunoassay for carcinoembryonic antigen and alpha-fetoprotein using electrochemical detection.

An MCE electrochemical enzyme immunoassay protocol for the determination of carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was reported. Two antigens (Ag), CEA and AFP, were incubated simultaneously with an excess amount of horseradish peroxidase-labeled antibody (Ab(*)). The free Ab(*) and the Ab(*)-Ag complex produced in the solution were first separated through a postcolumn reaction and then traced by the enzyme substrate o-aminophenol. The 3-aminophenoxazine produced in enzyme reaction was detected with downstream amperometric detection. The separations were performed at a separation voltage of +1.4 kV and were completed in less than 60 s. The better analytical performance and distinct miniaturization/portability for MCE at less assay time and sample volume consumption was achieved. The detection limit of CEA and AFP was calculated to be 0.25 and 0.13 ng/mL, respectively. Therefore, MCE could be used as a sensitive and new tool in separation science and offered considerable promise in biological sample analysis or quick clinical diagnosis.

The multiple antigen blot assay: a simple, versatile and multipurpose immunoenzymatic technique.

This technique is based on the sensitization of different antigens in a single nitrocellulose strip, which react when exposed to an immune serum and thereafter with the appropriate peroxidase conjugate and the corresponding substrate. Signals in those reactive spots are recorded as black squares in a negative photographic film, using a chemiluminiscent substrate or as blue spots when a precipitable colorimetric substrate is used. This technique allows the simultaneous demonstration of antigenicity of different antigens (peptides, recombinant molecules, and crude preparations), with a high sensitivity and specificity. Its major value is based on its versatility, since it is possible to rapidly evaluate and to compare various antigenic preparations and to use it for diagnosis of different infectious, allergic and autoimmune diseases, at a low cost.

Field Validation of Limiting-Antigen Avidity Enzyme Immunoassay to Estimate HIV-1 Incidence in Cross-Sectional Survey in Swaziland.

Reliable and accurate laboratory assays to detect recent HIV-1 infection have potential as simple and practical methods of estimating HIV-1 incidence in cross-sectional surveys. This study describes validation of the limiting-antigen (LAg) avidity enzyme immunoassay (EIA) in a cross-sectional national survey, conducted in Swaziland, comparing it to prospective follow-up incidence. As part of the Swaziland HIV-1 Incidence Measurement Survey (SHIMS), 18,172 individuals underwent counseling and HIV rapid testing in a household-based, population survey conducted from December 2010 to June 2011. Plasma samples from HIV-positive persons were classified as recent infections using an incidence testing algorithm with LAg-Avidity EIA (normalized optical density ≤1.5) followed by viral load (VL ≥1,000 copies/mL). All HIV-seronegative samples were tested for acute HIV-1 infection by nucleic acid amplification test (NAAT) pooling. HIV-seronegative individuals who consented to follow-up were retested ∼6 months later to detect observed HIV-1 seroconversion. HIV-1 incidence estimates based on LAg+VL and NAAT were calculated using assay-specific parameters and were compared with prospective incidence estimate. A total of 5,803 (31.9%) of 18,172 survey participants tested HIV seropositive; of these 5,683 (97.9%) were further tested with LAg+VL algorithm. The weighted annualized incidence from the longitudinal cohort study was 2.4% (95% confidence interval 2.0-2.7). Based on cross-sectional testing of HIV positives with LAg+VL algorithm, overall weighted annualized HIV-1 incidence was 2.5% (2.0-3.0), whereas NAAT-based incidence was of 2.6%. In addition, LAg-based incidence in men (1.8%; 1.2-2.5) and women (3.2%; 2.4-3.9) were similar to estimates based on observed incidence (men = 1.7%, women = 3.1%). Changes in HIV-1 incidence with age in men and women further validate plausibility of the algorithm. These results demonstrate that the LAg EIA, in a serial algorithm with VL, is a cost-effective tool to estimate HIV-1 incidence in cross-sectional surveys.

The Halogen assay--a new technique for measuring airborne allergen.

The Halogen assay is a new technique for measuring airborne allergen. The assay is unique in that it is capable of analyzing allergens and particles together, combining the advantages of morphological approaches and immunoassay. The Halogen assay allows direct observation of the particles that carry the allergen as well as being capable of identifying all the allergen sources an individual is exposed and sensitized to. The assay is sensitive because the extracted allergen is bound to the membrane at a high local concentration within the minute area around each particle and so is easily detected by immunostaining. It is therefore easy to detect few pollen grains. The Halogen method supersedes other methods commonly used to identify allergens as it is capable of identifying airborne particles that are allergen sources.

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.

Squamous cell carcinoma antigen in follow-up of cervical cancer treated with radiotherapy: evaluation of cost-effectiveness.

PURPOSE: The squamous cell carcinoma (SCC) antigen is still considered the most accurate serologic tumor marker in cervical carcinoma. We assessed the contribution of the SCC assay to the detection of recurrences in patients treated with radiotherapy. METHODS AND MATERIALS: The pattern of recurrence and follow-up data were prospectively recorded for 135 patients. Of the 135 patients, 103 (76.3%) had primary cervical carcinoma and 32 (23.7%) had already experienced disease recurrence that had been successfully treated with surgery (n = 2), surgery plus radiotherapy (n = 2), radiotherapy (n = 5), or concomitant chemoradiotherapy (n = 23). The follow-up evaluations (chest X-ray, abdominopelvic magnetic resonance imaging, gynecologic examination with colposcopy, Papanicolaou smear, and SCC assay) were performed at 6-month intervals; the evaluation was done earlier if recurrent disease was suspected. The median follow-up time was 29 months (range, 6-131). The SCC serum levels were assayed, and a cost analysis was done. RESULTS: A total of 481 SCC determinations were performed. Of the 135 patients, 43 (31.8%) experienced disease recurrence. The SCC levels were higher in those with recurrent disease than in the disease-free patients. Elevation of SCC was documented in 34 (79.1% sensitivity) of 43 recurrences before symptoms appeared. Of the 38 patients with serum SCC elevation, 34 developed a recurrence (positive predictive value, 89.5%). Of the 97 patients with negative SCC serum levels, 88 had negative findings at the clinicoradiologic evaluation (negative predictive value, 90.7%). A simplified approach (SCC plus gynecologic examination) was evaluated. Compared with the complete follow-up program, the rate of missed recurrence was 2.2%. The total projected cost per patient for 5 years of follow-up for the simplified procedure was approximately 12.2-fold lower than the standard approach. CONCLUSIONS: Our results have shown that a simplified diagnostic approach, including the SCC assay and gynecologic examination, can detect a high rate of recurrence from cervical cancer, with a very favorable cost-effective profile.

Strategies to improve the efficiency of celiac disease diagnosis in the laboratory.

The demand for testing to detect celiac disease (CD) autoantibodies has increased, together with the cost per case diagnosed, resulting in the adoption of measures to restrict laboratory testing. We designed this study to determine whether opportunistic screening to detect CD-associated autoantibodies had advantages compared to efforts to restrict testing, and to identify the most cost-effective diagnostic strategy. We compared a group of 1678 patients in which autoantibody testing was restricted to cases in which the test referral was considered appropriate (G1) to a group of 2140 patients in which test referrals were not reviewed or restricted (G2). Two algorithms A (quantifying IgA and Tissue transglutaminase IgA [TG-IgA] in all patients), and B (quantifying only TG-IgA in all patients) were used in each group, and the cost-effectiveness of each strategy was calculated. TG-IgA autoantibodies were positive in 62 G1 patients and 69 G2 patients. Among those positive for tissue transglutaminase IgA and endomysial IgA autoantibodies, the proportion of patients with de novo autoantibodies was lower (p=0.028) in G1 (11/62) than in G2 (24/69). Algorithm B required fewer determinations than algorithm A in both G1 (2310 vs 3493; p<0.001) and G2 (2196 vs 4435; p<0.001). With algorithm B the proportion of patients in whom IgA was tested was lower (p<0.001) in G2 (29/2140) than in G1 (617/1678). The lowest cost per case diagnosed (4.63 euros/patient) was found with algorithm B in G2. We conclude that opportunistic screening has advantages compared to efforts in the laboratory to restrict CD diagnostic testing. The most cost-effective strategy was based on the use of an appropriate algorithm.

Development and validation of an immunoperoxidase antigen detection test for improved diagnosis of rabies in Indonesia.

Rabies continues to pose a significant threat to human and animal health in regions of Indonesia. Indonesia has an extensive network of veterinary diagnostic laboratories and the 8 National laboratories are equipped to undertake diagnostic testing for rabies using the commercially-procured direct fluorescent antibody test (FAT), which is considered the reference (gold standard) test. However, many of the Indonesian Provincial diagnostic laboratories do not have a fluorescence microscope required to undertake the FAT. Instead, certain Provincial laboratories continue to screen samples using a chemical stain-based test (Seller's stain test, SST). This test has low diagnostic sensitivity, with negative SST-tested samples being forwarded to the nearest National laboratory resulting in significant delays for completion of testing and considerable additional costs. This study sought to develop a cost-effective and diagnostically-accurate immunoperoxidase antigen detection (RIAD) test for rabies that can be readily and quickly performed by the resource-constrained Provincial laboratories. This would reduce the burden on the National laboratories and allow more rapid diagnoses and implementation of post-exposure prophylaxis. The RIAD test was evaluated using brain smears fixed with acetone or formalin and its performance was validated by comparison with established rabies diagnostic tests used in Indonesia, including the SST and FAT. A proficiency testing panel was distributed between Provincial laboratories to assess the reproducibility of the test. The performance of the RIAD test was improved by using acetone fixation of brain smears rather than formalin fixation such that it was of equivalent accuracy to that of the World Organisation for Animal Health (OIE)-recommended FAT, with both tests returning median diagnostic sensitivity and specificity values of 0.989 and 0.993, respectively. The RIAD test and FAT had higher diagnostic sensitivity than the SST (median = 0.562). Proficiency testing using a panel of 6 coded samples distributed to 16 laboratories showed that the RIAD test had good reproducibility with an overall agreement of 97%. This study describes the successful development, characterisation and use of a novel RIAD test and its fitness for purpose as a screening test for use in provincial Indonesian veterinary laboratories.

Hepatitis B surface antigen detection using pooled sera. A cost-benefit analysis.

OBJECTIVES: To examine the feasibility and to perform a cost benefit analysis of a 5-sample pooling strategy using an enzyme immunoassay (EIA) for the screening of hepatitis B surface antigen (HBsAg). MATERIAL AND METHODS: To assess the sensitivity and specificity of the pooling method, each of the 40 positive sera (from weak to intensely HBsAg-positive) and 250 negative sera were tested in a pool with 4 HBsAg-negative sera. The limit of detection for HBsAg/ad and HBsAg/ay was evaluated using sera from a panel of purified subtypes. A study under real conditions was conducted using pools from 340 pregnant women. RESULTS: The sensitivity and specificity of this technique were 100%. The correlation coefficient among the sample/cutoff ratios of 40 samples studied in single and in pooled conditions was 0.792 (p < 0.005). The pooling method has lower levels of detection for HBsAg/ad and HBsAg/ay at 0.20 ng/mL and 0.12 ng/mL, and the single method at 0.34 ng/mL and 0.29 ng/mL, respectively. The pooling method loses no sensitivity for values up to 100 IU/L of anti-HBs in the four sera mixed with a positive serum. The cost-benefit analysis showed that the pooling method could save from 30% up to 75% of the cost of HBsAg determination, according to whether seroprevalences were 10% or 1%, respectively. CONCLUSIONS: The pooled HBsAg EIA yielded no worse than the single EIA test, and was a cost-effective and valid strategy in areas with a high, medium or low prevalence.

Newborn screening for cystic fibrosis.

Since the late 1970s when the potential of the immunoreactive trypsinogen assay for early identification of infants with cystic fibrosis was first recognised, the performance of newborn blood spot screening (NBS) has been continually assessed and its use has gradually expanded. NBS for cystic fibrosis is a cost-effective strategy and, if standards of care are fully implemented and robust management pathways are in place, has a positive effect on clinical outcomes. In the past decade, NBS has undergone rapid expansion and an unprecedented number of infants with cystic fibrosis have access to early diagnosis and care. Cystic fibrosis NBS has now moved on from the development phase and is entering an era of consolidation. In the future, research should focus on the rationalisation and optimisation of existing programmes, with particular attention to bioethical implications such as unwanted detection of carriers and inconclusive diagnoses.

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.

The cost-effectiveness of expanded testing for primary HIV infection.

PURPOSE: Primary infection with the human immunodeficiency virus (HIV) is a major factor in the HIV epidemic. Most patients become symptomatic and seek care, but seldom are they tested or is their condition diagnosed. The objectives of this study are to determine whether it is cost-effective to expand testing for primary HIV infection to a larger cohort of patients, and, if so, which diagnostic assay is most cost-effective. METHODS: We undertook a cost-effectiveness analysis of testing a hypothetical cohort of more than 3 million outpatients with fever and other viral symptoms regardless of HIV risk factors using 3 diagnostic assays: p24 antigen enzyme immunosorbent assay (EIA), HIV-1 RNA assay, and third-generation HIV-1 EIA. Antiretroviral therapy was started when the CD4 cell count decreased to 350/microL. Outcome measures were the incremental cost-effectiveness of the diagnostic assays, number of cases identified, cases avoided in sexual partners, and threshold prevalence. For sensitivity analyses, we used 50,000 dollars as the threshold for cost-effectiveness. RESULTS: At the baseline prevalence of 0.66%, p24 antigen EIA testing was the most cost-effective option at a cost of 30,800 dollars per quality-adjusted life-year gained when compared with no testing. There were 17,054 cases identified, and infection was avoided in 435 partners. Probabilistic sensitivity analysis, in which the estimates for all variables are varied simultaneously, determined that expanded testing with p24 antigen EIA compared with no testing had a 67% probability of being cost-effective at the baseline prevalence and a 71% probability at a prevalence of 1%. CONCLUSIONS: Expanded testing for primary HIV infection with p24 antigen EIA may be a sound expenditure of health care resources.

[New methodological advances: algorithm proposal for management of Clostridium difficile infection]. / Nuevos avances metodológicos: propuesta de algoritmo para el manejo de la infección por Clostridium difficile.

INTRODUCTION: Clostridium difficile infection (CDI) is considered the most common cause of health care-associated diarrhea and also is an etiologic agent of community diarrhea. The aim of this study was to assess the potential benefit of a test that detects glutamate dehydrogenase (GDH) antigen and C. difficile toxin A/B, simultaneously, followed by detection of C. difficile toxin B (tcdB) gene by PCR as confirmatory assay on discrepant samples, and to propose an algorithm more efficient. MATERIAL AND METHODS: From June 2012 to January 2013 at Hospital Infantil Universitario Niño Jesús, Madrid, the stool samples were studied for the simultaneous detection of GDH and toxin A/B, and also for detection of toxin A/B alone. When results between GDH and toxin A/B were discordant, a single sample for patient was selected for detection of C. difficile toxin B (tcdB) gene. RESULTS: A total of 116 samples (52 patients) were tested. Four were positive and 75 negative for toxigenic C. difficile (Toxin A/B, alone or combined with GDH). C. difficile was detected in the remaining 37 samples but not toxin A/B, regardless of the method used, except one. Twenty of the 37 specimens were further tested for C. difficile toxin B (tcdB) gene and 7 were positive. DISCUSSION: The simultaneous detection of GDH and toxin A/B combined with PCR recovered undiagnosed cases of CDI. In accordance with our data, we propose a two-step algorithm: detection of GDH and PCR (in samples GDH positive). This algorithm could provide a superior cost-benefit ratio in our population.