A rapid, sensitive and reliable diagnostic test for scrub typhus in China

Purpose: To evaluate the performances for detection of IgM and IgG antibodies to Orientia. tsutsugamushi (Ot) using a gold conjugate-based rapid diagnostic test (RDT). Materials and Methods: The RDT employing mixture recombinant 56-kDa proteins of O. tsutsugamushi and the mIFA assay was performed on 33 patients from Fujian and Yunnan province respectively and 94 positive sera (36 from Hainan province and 58 from Jiangsu province) from convalescent stages of the patients with scrub typhus respectively and 82 negative sera from healthy farmers from Anhui province and Beijing City respectively in 2009. A comparison of the RDT and mIFA assay was performed by using the χ² test and the P level of ≤0.05 was considered to be significant. Results: Among these 94 positive sera from convalescent stages of the illness and 82 sera from control farmers, the specificity of RDT was 100% for both IgM and IgG tests. In 33 cases with scrub typhus, 5 cases were positively detected earlier by RDT than by mIFA for the IgM test, and 2 cases were positive for the IgG test. The sensitivities of RDT were 93.9% and 90.9% for IgM and IgG, respectively. Considering IgM and IgG together, the sensitivity was 100%. The geometric mean titre (GMT) of IFA and the RDT assay in diluted sera from confirmed cases were 1:37 versus 1:113 respectively (P<0.001) for IgM test and 1:99 versus 1:279 respectively (P<0.016) for IgG. Conclusions: The RDT was more sensitive than the traditional IFA for the early diagnosis of scrub typhus and was particularly suitable for use in rural areas.     

Diagnostic accuracy of antibody-based rapid diagnostic tests in detecting coronavirus disease 2019: systematic review

IntroductionThe rapid transmission of coronavirus disease 2019 (COVID-19) requires a fast, accurate, and affordable detection method. Despite doubts of their diagnostic accuracy, rapid diagnostic tests (RDTs) are used worldwide due to their practicality. This systematic review aims to determine the diagnostic accuracy of antibody-based RDTs in detecting COVID-19.Material and methodsA literature search was carried out on five journal databases using the PRISMA-P 2015 method. We included all studies published up to February 2021. The risk of bias was evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Diagnostic Test Accuracy Studies. Data regarding peer-review status, study design, test kit information, immunoglobulin class, target antigen, and the number of samples were extracted and tabulated. We estimated the pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) with a 95% confidence interval.ResultsThirty-three studies met the eligibility criteria. The pooled data results showed that the combined detection method of IgM or IgG had the highest sensitivity and NPV, which were 73.41% (95% CI: 72.22–74.57) and 75.34% (95% CI: 74.51–76.16), respectively. The single IgG detection method had the highest specificity and PPV of 96.68% (95% CI: 96.25–97.07) and 95.97% (95% CI: 95.47–96.42%), respectively.ConclusionsAntibody-based RDTs are not satisfactory as primary diagnostic tests but have utility as a screening tool.     

Evaluation of the diagnostic performance and operational characteristics of four rapid immunochromatographic syphilis tests in Burkina Faso

Background and objective

Little information is available on the rapid diagnostic testing for syphilis in Burkina Faso. The objectives of the study were (i) to assess the sensitivity and specificity of four on site rapid tests in comparison with Treponema pallidum haemagglutination assay (TPHA) as a gold standard and (ii) to evaluate the operational characteristics of those tests among health workers in a maternity unit.

Methods

Four rapid syphilis tests commercially available in Burkina Faso were evaluated using archived serum samples and Treponema pallidum hemagglutination assay (TPHA) as the gold standard. Blood samples were collected between November 2011 and June 2012 from blood donors at the Regional Blood Transfusion Center of Ouagadougou. The sensitivity and specificity of the tests were calculated. Evaluation of operational characteristics such as clarity of pamphlet, complexity of technique, duration, was conducted in a first-level healthcare center with health workers in maternity unit.

Results

Alere DetermineTM Syphilis was the most sensitive of the four rapid syphilis tests evaluated. It was followed by SD Bioline Syphilis 3.0, Cypress Diagnostics Syphilis Quick test and Accu-Tell ® Rapid Anti-TP, which was the least sensitive. The four tests demonstrated a good diagnostic specificity for syphilis (95–98%), and healthcare workers found them easy to use.

Conclusions

The study allowed confirming the good performance of three of four rapid syphilis tests in Burkina Faso. More research will be conducted to assess the feasibility of introducing selected rapid tests for syphilis in antenatal care services.     

山西某县HIV/HCV感染调查的实验室质量控制

目的 分析山西某县开展HIV/HCV调查的实验室质量控制方法,探讨质控对调查准确性的影响.方法 在整个调查中对现场的HIV、HCV检测实施插入质控品及样本抽检的质控方案.根据预调查质控结果,通过增加人员培训、加强考核频次、提高抽检比例等手段调整质控方案用于主调查.结果 HIV感染预调查,现场的插入质控品检测和抽检结果与...     

Comparison of three real-time PCR methods with blood smears and rapid diagnostic test in Plasmodium sp. infection

In cases of malaria, rapid and accurate diagnosis of Plasmodium sp. is essential. In this study three different quantitative, real-time PCR methods were compared with routine methods used for malaria diagnosis. A comparative study was conducted prospectively in the laboratories of Montpellier and Nîmes University Hospitals. The methods used for routine diagnostic malaria testing consisted of microscopic examination of Giemsa-stained blood smears and rapid diagnostic tests. Three quantitative real-time PCR methods (qRT-PCR) were tested: qRT-PCR1 amplified a specific sequence on the P. falciparum Cox1 gene, qRT-PCR2 amplified a species-specific region of the multicopy 18S rDNA, and qRT-PCR3 amplified a mitochondrial DNA sequence. Among the 196 blood samples collected, 73 samples were positive in at least one of the five tests. Compared with the routine method, there were no false negatives for P. falciparum diagnosis in either qRT-PCR1 or qRT-PCR3. In all P. ovale, P. vivax and P. malariae infections diagnosed from blood smears, qRT-PCR1 was negative, as expected, whereas qRT-PCR2 and qRT-PCR3 were positive and concordant (simple κ coefficient = 1). One negative sample from microscopy was positive with both qRT-PCR2 and qRT-PCR3. Together, qRT-PCR3 and the combined qRT-PCR1 and qRT-PCR2 were concordant with routine methods for malaria diagnosis (99% and 99.5%, respectively). These three rapid, molecular qRT-PCR methods, used alone or in association, showed excellent results, with high concordance, accuracy and reliability in malaria diagnosis.     

Evaluation of performance testing of different rapid diagnostic kits in comparison with EIAs to validate detection of hepatitis B virus among high risk group in Nigeria

Background: Hepatitis B virus (HBV) causes chronic liver-associated diseases and its early detection is of high public health importance. Its diagnosis is mainly based on immunological assays among which Enzyme-Linked Immunosorbent Assay (ELISA) and rapid tests are the most common and widespread methods. However, a major challenge is the discordance of results of any two laboratory assays which cannot be easily resolved. Therefore, this study was designed to evaluate the validity and reliability of commercially available five rapid test kits in comparison with two Enzyme Immunoassays (EIAs) in Nigeria using hepatitis B surface antigen as a reference marker.

Methods: A total of 100 sera of previously diagnosed consenting HBV-positive patients from private diagnostic laboratories in Ibadan between March and August, 2011 were tested using two EIA and five rapid commercially available HBV test kits in Nigeria. Data were analyzed by SPSS version 15, while bivariate and multivariate analyses were carried out to identify associations at P < 0.05 considered significant.

Results: Overall, the sensitivity rates of the two EIA kits were 100% and 99.9% (95% confidence interval [CI] = 98.9–99.7) with specificity of 100% and 99.9% (95% CI = 98.9–99.7), respectively. The sensitivity of the five rapid test kits ranged from 97.5% (95% CI = 96.4–97.6) to 98.9% (95% CI = 97.9–99.9) with specificity of 80% (95% CI = 79.3–80.9) to 90% (95% CI = 89.2–91.0). Also, the positive predictive value ranged from 88% (95% CI = 88.2–89.9) to 89% (95% CI = 88.2–89.9), while the negative predictive value ranged from 80% (95% CI = 79.3–80.9) to 90% (95% CI = 89.2–91.0) for the five rapid kits. However, that of the two EIAs ranged from 99.9% (98.9–99.7) to 100%. Further analysis showed significant (P = 0.033) variations in the sensitivity and specificity of the EIAs and rapid test kits.

Conclusions: The results from this study have clearly revealed the challenges of diagnosis of HBV infections in Nigeria. This study has also demonstrated that the sensitivity of most of the rapid test kits may not be adequate when compared with EIA for early detection of HBV infections. The implications of possible misdiagnosis on the various intervention strategies that rely predominantly on correct HBV status of an individual are enormous. Therefore, there is the need to further compliment the use of rapid test kits with EIAs for HBV control in Nigeria.     

Screening of blood from potential organ and cornea donors for viruses

Prospective nucleic acid tests were carried out for human immunodeficiency virus (HIV) and hepatitis C virus (HCV) using the COBAS Amplicor HIV-1 and HCV tests (Roche Diagnostics, Meylan, France) on potential organ (n=113) and cornea (n=368) donors in France to evaluate their performance and suitability for use as a complement to routine serological tests. Blood samples were collected from organ donors with preserved cardiac function after verification of cerebral death. Blood samples were collected from cornea donors post-mortem within 48 hr after death. An internal control was added to the samples before extraction to monitor each individual polymerase chain reaction (PCR). The nucleic acid tests were always interpretable in organ donors and negative in all except in 2 anti-HCV positive patients. One had an indeterminate HIV p24 antigen but was negative for HIV RNA. HIV and HCV RNA were not found in cornea donors with a negative serology but indeterminate molecular results were frequent in this group (17.6%). Cornea donors also gave significantly more (14.4%) indeterminate serological results than organ donors (1.8%) (P<0.001). This was due to the poor quality of the blood samples collected post-mortem. However, there was no correlation between indeterminate results of serological and molecular tests. There were 16/19 (84%) indeterminate serological results for HIV and 4/4 (100%) for HCV that were negative by PCR. Thus, nucleic acid tests could be useful for qualifying a donor whose serological results are indeterminate. The extraction procedures on post-mortem specimens and/or blood collection must be changed to improve the performance of nucleic acid tests.     

Predictive,pre-natal and diagnostic genetic testing for Huntington's disease: the experience in Canada from 1987 to 2000

Predictive and pre-natal testing for Huntington's Disease (HD) has been available since 1987. Initially this was offered by linkage analysis, which was surpassed by the advent of the direct mutation test for HD in 1993. Direct mutation analysis provided an accurate test that not only enhanced predictive and pre-natal testing, but also permitted the diagnostic testing of symptomatic individuals. The objective of this study was to investigate the uptake, utilization, and outcome of predictive, pre-natal and diagnostic testing in Canada from 1987 to April 1, 2000. A retrospective design was used; all Canadian medical genetics centres and their affiliated laboratories offering genetic testing for HD were invited to participate. A total of 15 of 22 centres (68.2%), currently offering or ever having offered genetic testing for HD, responded, providing data on test results, demographics, and clinical history. A total of 1061 predictive tests, 15 pre-natal tests, and 626 diagnostic tests were performed. The uptake for predictive testing was approximately 18% of the estimated at-risk Canadian population, ranging from 12.5% in the Maritimes to 20.7% in British Columbia. There appears to have been a decline in the rate of testing in recent years. Of the predictive tests, 45.0% of individuals were found to have an increased risk, and a preponderance of females (60.2%) sought testing. A greater proportion of those at < or = 25% risk sought predictive testing once direct CAG mutation analysis had become available (10.9% after mutation analysis vs 4.7% before mutation analysis, p = 0.0077). Very few pre-natal tests were requested. Of the 15 pre-natal tests, 12 had an increased risk, resulting in termination of pregnancy in all but one. Diagnostic testing identified 68.5% of individuals to be positive by mutation analysis, while 31.5% of those with HD-like symptoms were not found to have the HD mutation. The positive diagnostic tests included 24.5% of individuals with no known prior family history of HD.     

Rapid diagnostic testing of methicillin-resistant Staphylococcus aureus carriage at different anatomical sites: costs and benefits of less extensive screening regimens

Multiple body site screening and pre-emptive isolation of patients at risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage are considered essential for control of nosocomial spread. The relative importance of extranasal screening when using rapid diagnostic testing (RDT) is unknown. Using data from a multicentre study evaluating BD GeneOhm? MRSA PCR (IDI), Xpert MRSA (GeneXpert) and chromogenic agar, added to conventional cultures, we determined cost-effectiveness assuming isolation measures would have been based on RDT results of different hypothetical screening regimes. Costs per isolation day avoided were calculated for regimes with single or less extensive multiple site RDT, regimes without conventional back-up cultures and when PCR would have been performed with pooling of swabs. Among 1764 patients at risk, MRSA prevalence was 3.3% (n = 59). In all scenarios the negative predictive value is above 98.4%. With back-up cultures of all sites as a reference, the costs per isolation day avoided were £15.19, £30.83 and £45.37 with ‘nares only’ screening using chromogenic agar, IDI and GeneXpert, respectively, as compared with £19.95, £95.77 and £125.43 per isolation day avoided when all body sites had been screened. Without back-up cultures costs per isolation day avoided using chromogenic agar would range from £9.24 to £76.18 when costs per false-negative RDT range from £5000 up to £50 000; costs for molecular screening methods would be higher in all scenarios evaluated. In conclusion, in a low endemic setting chromogenic agar screening added to multiple site conventional cultures is the most cost-effective MRSA screening strategy.     

Postmortem blood tests for HIV,HBV, and HCV in a body donation program

A retrospective analysis of the results of blood tests conducted on body donors received by the Anatomical Gift Registry of the Medical College of Wisconsin (MCW) was performed. Over the 5-year period from April 1992 through March 1997 a total of 785 body donors were tested for Human Immunodeficiency Virus (HIV) and Hepatitis B and C Viruses (HBV and HCV). Eighteen of the 785 donors (2.3%) tested positive for one of these infectious agents. Two donors were positive for HIV, six were positive for HBV and ten were positive for HCV. The death certificates and files of those donors who tested positive were reviewed and the results are presented here. Blood testing prior to the use of the body donors is an effective and reasonable way of identifying the presence of these infectious agents, thus reducing the risk to those who work with cadavers. The cost for the testing at MCW is about $60 per donor. Clin. Anat. 11:250–252, 1998. © 1998 Wiley-Liss, Inc.     

Detection of cytomegalovirus DNA on dried blood spots collected from infants infected with HIV: An in-house method adaptable in resource-limited settings

In countries with limited resources, infants infected with HIV are highly exposed to CMV co-infection which probably represents a major risk factor for disease progression in this population. This study aimed to evaluate the performance of a low cost CMV DNA extraction method from DBS and the feasibility of its implementation in laboratories of 4 countries with limited resources. DNA was extracted from DBS with a cationic resin (chelex 100) and amplified with an “in house” real time CMV PCR. Dilutions of a quantified whole blood sample were spotted on paper to evaluate the 95% detection limit. A DBS quality control panel was analyzed in all laboratories. CMV PCR was compared between DBS and liquid whole blood (gold standard) in 2 populations: 418 transplanted patients and 59 infants infected with HIV (median age of 2 months). The CMV PCR 95% detection limit in DBS was 3.87 log₁₀ copies/mL. Its positive and negative predictive values for CMV diagnosis in infants infected with HIV were 100% and 87.5% respectively. Quality control panels gave consistent qualitative results in all laboratories. This assay had high predictive values for CMV diagnosis in infants infected with HIV and its implementation in resource-limited countries with limited resources is feasible.     

Universal screening versus universal precautions in the context of preoperative screening for HIV,HBV, HCV in India

In the Indian context, there is a convention of doing pre-operative screening for HIV, hepatitis B virus and hepatitis C viruses for all patients as a routine pre-intervention investigation. This approach is justified in some instances in the best interest of the patient. However, as routine screening is not the standard care internationally and as there is a significant divergence of views about the merits and demerits of this practice, this issue needs to be debated in a rational manner with an evidence-based approach. The present article is authored by a surgeon and a microbiologist from a new cancer care centre in eastern India, who has attempted to address this contentious issue. The various available options have been explored, and advantages and disadvantages of the different approach have been discussed. An algorithm for infection prevention and control has been presented so that surgeons and medical microbiologists could manage infection control challenges satisfactorily.     

Use of MALDI-TOF MS technique for rapid identification of bacteria from positive blood cultures

We evaluated the feasibility of same-day routine aerobic bacterial identification using the following procedures: Picking colonies from 4 and 6 h incubated subculture from positive blood culture bottle and analyzing them by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). The matched identification rate of this procedure at the species level was 80.6% (141/175) for the 4-h cultures compared with overnight cultures and 90.9% (159/175) for the 6-h cultures. Thus, our technique provides an easy and rapid method for identification of aerobic bacteria in routine clinical microbiology laboratories.     

Seroprevalence of six different viruses among pregnant women and blood donors in rural and urban Burkina Faso: A comparative analysis

A seroprevalence study was carried out of six different human pathogenic viruses, namely human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-cell leukemia virus (HTLV), human herpesvirus type 8 (HHV-8), and dengue virus among pregnant women and blood donors from rural (Nouna) and urban (Ouagadougou) Burkina Faso, West Africa. A total of 683 samples from blood donors (n = 191) and pregnant women (n = 492) were collected from both sites and screened for the different virus infection markers resulting in the following prevalence values for Nouna or Ouagadougou, respectively: HIV 3.6/4.6, anti-HBV core (anti-HBc) 69.6/76.4, HBV surface antigen (HBsAg)14.3/17.3, HCV 2.2/1.5, HTLV 1.4/0.5, HHV-8 11.5/13.5, dengue virus 26.3/36.5. Individuals aged > or =25 years were more likely to be infected with HIV than those below 24 years (P < 0.05). Infection with HIV increased the likelihood of co-infection with other viruses, such as HHV-8, HBV and HTLV. Co-infection studies involving five viruses (HBV-HBsAg, HHV-8, HIV, HCV, and HTLV) showed that 4.8% (33/683) of the studied population were dually infected, with HBsAg+ HHV-8 (13/33), HBsAg+HIV (8/33) and HIV+HHV-8 (8/33) being the most common co-infections. Of the population studied 0.6% (4/683) was triply infected, the most common infection being with HBV+HIV+HHV-8 (3/4). There was no difference in the prevalence of HIV, anti-HBc, HBsAg, HCV, HTLV, and HHV-8 either among blood donors or pregnant women in urban or rural setting, while dengue virus prevalence was relatively lower in rural (26.3%) than in urban (36.5%) Burkina Faso.     

Application of SNP array for rapid prenatal diagnosis: implementation, genetic counselling and diagnostic flow

We report on the validation and implementation of the HumanCytoSNP-12 array (Illumina) (HCS) in prenatal diagnosis. In total, 64 samples were used to validate the Illumina platform (20 with a known (sub) microscopic chromosome abnormality, 5 with known maternal cell contamination (MCC) and 39 normal control samples). There were no false-positive or false-negative results. In addition to the diagnostic possibilities of arrayCGH, the HCS allows detection of regions of homozygosity (ROH), triploidy and helps recognising MCC. Moreover, in two cases of MCC, a deletion was correctly detected. Furthermore we found out that only about 50 ng of DNA is required, which allows a reporting time of only 3 days. We also present a prospective pilot study of 61 fetuses with ultrasound abnormalities and a normal karyotype tested with HCS. In 4 out of 61 (6.5%) fetuses, a clinically relevant abnormality was detected. We designed and present pre-test genetic counselling information on categories of possible test outcomes. On the basis of this information, about 90% of the parents chose to be informed about adverse health outcomes of their future child at infancy and childhood, and 55% also about outcomes at an adult stage. The latter issue regarding the right of the future child itself to decide whether or not to know this information needs to be addressed.     

Evaluation of rapid diagnostic tests for malaria in Swedish travellers

Rapid diagnostic tests (RDTs) for malaria have become valuable tools for the diagnosis of malaria in both endemic and non-endemic areas. During a 7-year period, first the MalaQuick rapid test and then the NOW Malaria test, were evaluated by well-trained laboratory technicians in a university hospital laboratory of parasitology. A total of 635 blood samples were selected from 4731 blood specimens obtained from travellers at the emergency department, at wards and at out-patient clinics. The samples were analysed by microscopy and RDT. Malaria parasites were detected in the blood films of 134 (21%) samples. The sensitivity of the RDT for Plasmodium falciparum was 97.7% (84 of 86 samples) with a negative predictive value of 99.6%. The two false-negative results were associated with low levels of parasitaemia. For non-falciparum species the sensitivity was only 58.3% (28 of 48 samples). Based on the excellent ability of the RDTs to detect P. falciparum infections, we recommend the use of the NOW Malaria test as a complement to microscopy in the laboratory.     

Molecular diagnostic yield of genome sequencing versus targeted gene panel testing in racially and ethnically diverse pediatric patients

PurposeAdoption of genome sequencing (GS) as a first-line test requires evaluation of its diagnostic yield. We evaluated the GS and targeted gene panel (TGP) testing in diverse pediatric patients (probands) with suspected genetic conditions.MethodsProbands with neurologic, cardiac, or immunologic conditions were offered GS and TGP testing. Diagnostic yield was compared using a fully paired study design.ResultsA total of 645 probands (median age 9 years) underwent genetic testing, and 113 (17.5%) received a molecular diagnosis. Among 642 probands with both GS and TGP testing, GS yielded 106 (16.5%) and TGPs yielded 52 (8.1%) diagnoses (P < .001). Yield was greater for GS vs TGPs in Hispanic/Latino(a) (17.2% vs 9.5%, P < .001) and White/European American (19.8% vs 7.9%, P < .001) but not in Black/African American (11.5% vs 7.7%, P = .22) population groups by self-report. A higher rate of inconclusive results was seen in the Black/African American (63.8%) vs White/European American (47.6%; P = .01) population group. Most causal copy number variants (17 of 19) and mosaic variants (6 of 8) were detected only by GS.ConclusionGS may yield up to twice as many diagnoses in pediatric patients compared with TGP testing but not yet across all population groups.     

Acceptability of counselling and testing for HIV infection in women in labour at the University College Hospital, Ibadan, Nigeria

Background

Many patients are referred to labour ward as emergencies, and therefore do not benefit from the antenatal HIV counselling and testing and treatment offered to registered patients.

Objective

To assess the acceptability and suitability of offering HIV counselling and testing to women of unknown HIV status presenting in labour.

Methods

A cross-sectional study comprising counselling and obtaining consent for HIV testing among 104 unregistered patients who presented in labour over a 3-month period. Rapid and enzyme-linked immunosorbent assay screening was performed for 90 consenting respondents. Reactive results were confirmed by Western blot. Appropriate therapy was instituted.

Results

Acceptance rate for HIV testing was 86.5%, prevalence of HIV was 6.7%. Women of lower educational status were more likely to accept testing in labour (OR: 0.3; 95% CI: 0.1–0.7; p=0.01); age, parity, occupation and knowledge of HIV had no influence. Most women (66.3%) had satisfactory knowledge of HIV. No one admitted to feeling coerced to test in fear of being denied care. Most refusals for screening were to avoid needle pricks (28.6%).Compared to ELISA screening test, specificity of the rapid test was 100%, sensitivity 85.7%, positive predictive value 100% and negative predictive value 98.8%. Attitude to testing was maintained on post-partum re-evaluation.

Conclusion

The prevalence of HIV amongst unregistered parturients showed the importance of offering point-of-care HIV testing and intervention, especially in an environment where antenatal clinic attendance is poor. Rapid testing appeared to be acceptable and feasible in labour to prevent the mother-to-child transmission of HIV.