A diagnostic evaluation of a molecular assay used for testing and treating anorectal chlamydia and gonorrhoea infections at the point-of-care in Papua New Guinea

ObjectivesPapua New Guinea has among the highest prevalences of sexually transmissible infections (STIs) globally with no services able to accurately test for anorectal Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections. Here we prospectively evaluated the diagnostic performance of a molecular CT/NG assay used at the point-of-care (POC) with the aim of enhancing anorectal STI screening and same-day treatment.MethodsMen who have sex with men, transgender women and female sex workers taking part in Papua New Guinea's first large-scale biobehavioural study were enrolled and asked to provide a self-collected anorectal swab for POC GeneXpert CT/NG testing. Same-day treatment was offered if positive. A convenience sample of 396 unique and randomly selected samples were transported to Australia for comparison using the Cobas 4800 CT/NG test (Roche Molecular Diagnostics, Pleasanton, CA, USA).ResultsA total of 326 samples provided valid results by Cobas whereas 70 samples provided invalid results suggesting inhibition. The positive, negative and overall percentage agreements of GeneXpert CT/NG for the detection of C. trachomatis were 96.7% (95% CI 92.3%–98.9%), 95.5% (95% CI 91.3%–98.0%) and 96.0% (95% CI 93.3%–97.8%), and for N. gonorrhoeae were 93.0% (95% CI 86.1%–97.1%), 100.0% (95% CI 98.3%–100.0%) and 97.8% (95% CI 95.6%–99.1%), respectively.ConclusionsThe overall rate of agreement between the GeneXpert and Cobas CT/NG assays was high with 96.0% for C. trachomatis and 97.8% for N. gonorrhoeae. Results from this study data suggest that the GeneXpert CT/NG assay is suitable for testing self-collected anorectal specimens at the POC and that same-day treatment was feasible.     

Diagnostic Accuracy of Xpert MTB/RIF Assay in Extrapulmonary Tuberculosis

Introduction: The WHO endorsed Xpert Mycobacterium tuberculosis/rifampicin (MTB/RIF) assay, has been evaluated for pulmonary TB in a number of studies but very few have investigated it for extrapulmonary specimens. The present study evaluates the performance of Xpert MTB/RIF assay in the diagnosis of extrapulmonary TB (EPTB). Aim and Objectives: The aim of the study is to determine sensitivity and specificity of Xpert MTB/RIF assay for diagnosis of EPTB and RIF resistance in comparison to culture on Lowenstein–Jensen (LJ) medium and proportion method (PM), respectively. Materials and Methods: A total of 738 specimens from clinically suspected cases of EPTB were subjected to Ziehl–Neelsen staining, Xpert MTB/RIF assay and culture on LJ medium. PM was done on MTB isolates. Results: The sensitivity, specificity of Xpert MTB/RIF assay for diagnosis of EPTB were 84.91% (95% confidence interval [CI] 72.41%–93.25%) and 86.72% (95% CI 83.94%–89.17%) and for RIF resistance detection were 60.00% (95% CI 32.29%–83.66%) and 94.74% (95% CI 73.97%–99.87%), respectively. Among culture-positive cases, the sensitivity of Xpert MTB/RIF assay was 94.12% in smear positive and 80.56% in smear-negative cases. Xpert MTB/RIF showed maximum sensitivity of MTB detection from lymph node specimens (100% [95% CI 54.07%–100.00%]) and other body fluids (100% [95% CI 15.81%–100.00%]). Conclusion: The present study establishes Xpert MTB/RIF assay as a promising tool in the rapid diagnosis of EPTB and detection of RIF resistance.     

Evaluation of the HISCL Anti-Treponema pallidum Assay as a Screening Test for Syphilis

The resurgence of syphilis in recent years has become a serious threat to public health worldwide, and the serological detection of specific antibodies against Treponema pallidum remains the most reliable method for laboratory diagnosis of syphilis. This study examined the performance of the recently launched HISCL anti-Treponema pallidum (anti-TP) assay as a screening test for syphilis in a high-volume laboratory. The HISCL anti-TP assay was tested in 300 preselected syphilis-positive samples, 704 fresh syphilis-negative samples, 48 preselected potentially interfering samples, and 30 “borderline” samples and was compared head to head with the commercially available Lumipulse G TP-N. In this study, the HISCL anti-TP assay was in perfect agreement with the applied testing algorithms with an overall agreement of 100%, comparable to that of Lumipulse G TP-N (99.63%). The sensitivity and specificity of the HISCL anti-TP assay were 100% (95% confidence interval [CI], 98.42% to 100%) and 100% (95% CI, 99.37% to 100%), respectively. Considering the excellent ease of use and automation, high throughput, and its favorable sensitivity and specificity, the HISCL anti-TP assay may represent a new choice for syphilis screening in high-volume laboratories.     

Using the AD12-ICT rapid-format test to detect Wuchereria bancrofti circulating antigens in comparison to Og4C3-ELISA and nucleopore membrane filtration and microscopy techniques

Lymphatic filariasis (LF) continues to be a major source of permanent disability and an impediment to socio-economic development in 73 countries where more than 1 billion people are at risk and over 120 millions are infected. The global drive to eliminate LF necessitates an increasing demand for valid, reliable and rapid diagnostic tests. This study aimed to assess the performance of the AD12 rapid format immunochromatographic test (ICT) to detect Wuchereria bancrofti circulating antigens, against the combined gold standard: TropBio Og4C3-ELISA (enzyme-linked immunosorbent assay) which detects circulating filarial antigen (CFA) and the nucleopore membrane filtration and microscopic examination. This prospective case-control study involved 647 asymptomatic migrant workers from filariasis-endemic countries. Of these specimens, 32 were positive for microfilaremia using the membrane filtration and microscopy, 142 positive by ELISA (of which 32 had microfilaremia), and 128 positive by the ICT (of which 31 had microfilaremia). The performance of the ICT was calculated against 32 true-positive and 90 true-negative cases. For the detection of CFA, the ICT had a sensitivity of 97% (95% confidence interval [CI] 91–103), specificity 100% (95% CI 100–100), Positive Predictive Value (PPV) 100% (95% CI 100–100), Negative Predictive Value (NPV) 99% (95% CI 97–101); and the total accuracy of the test was 99% (95% CI 98–101). The agreement between ICT and ELISA in detecting W. bancrofti antigens was excellent (kappa?=?0.934; p?=?0.000). In conclusion, the AD12-ICT test for the detection of W. bancrofti-CFA was sensitive and specific and comparable to the performance of ELISA. The ICT would be a useful additional test to facilitate the proposed strategies for control and elimination of LF. Because it is rapid, simple to perform, and does not require the use of special equipment, the ICT may be most appropriate in screening programs and in monitoring the possible risk of introducing the disease to the non-endemic countries.     

Successful nanolitre real-time PCR detection of respiratory pathogens in clinical specimens

We performed a proof-of-concept study to determine if human pathogens could be detected in clinical specimens using nanolitre-volume real-time PCR. Nanolitre PCR for Bordetella pertussis/ B. parapertussis and respiratory syncytial virus (RSV) was performed on nasopharyngeal specimens and results compared with conventional methods. B. pertussis/B. parapertussis nanolitre PCR detection was 100% sensitive (20/20; 95% CI, 84–100%) and 100% specific (26/26; 95% CI, 87–100%). RSV nanolitre PCR was also 100% sensitive (21/21; 95% CI, 85–100%) and specific (25/25; 95%, CI 87–100%). Respiratory pathogens can be successfully detected in clinical specimens using nanolitre-volume PCR.     

Comparison of Xpert Norovirus and RidaGene Norovirus assays for the detection of noroviruses in clinical fecal specimens

The purpose of this study was to investigate the usability and performance of the Xpert Norovirus and RidaGene Norovirus assays for the detection of noroviruses in fecal specimens. Of the 186 stool specimens, 53 (28.5%) were considered true-positive for norovirus (NoV). Of the true-positive specimens, Xpert detected 53 and RidaGene detected 52. The respective sensitivity and specificity were 100% and 94.7% [95% confidence interval (CI), 91.0–98.5%] for the Xpert assay, and 98.1% (95% CI, 94.4–100%) and 97.0% (95% CI, 94.1–99.9%) for the RidaGene assay. Positive and negative predictive values (PPVs and NPVs) were 88.3% and 100% for the Xpert assay, and 92.9% and 99.2% for the RidaGene assay, respectively. Based on this study, it can be concluded that there were no significant differences (p-value?>?0.5) between the results of the Xpert and RidaGene Norovirus assays. We found that both assays are useful for the detection of noroviruses in clinical stool samples.     

Evaluation of four commercial real-time PCR assays for the detection of lymphogranuloma venereum in Chlamydia trachomatis-positive anorectal samples

ObjectivesLymphogranuloma venereum (LGV) is a sexually transmitted infection (STI) caused by Chlamydia trachomatis (CT) genovars L. The identification of LGV is of therapeutic interest because treatment requires 3 weeks of doxycycline compared with 1 week for infection with a non-L strain. The aim of this study was to evaluate the performance of four commercial real-time PCR kits in comparison with the reference methods used for LGV diagnosis by the French National Reference Centre (NRC) for bacterial STIs.MethodsA total of 215 French CT-positive anorectal specimens collected consecutively in 2017 were used (66 LGV and 149 non-LGV). Among these, 92 were collected from symptomatic men who have sex with men (MSM) and 123 from asymptomatic MSM using pre-exposure prophylaxis. Four commercial assays were evaluated; a single-plex assay RealCycler CHSL kit (Progenie Molecular), tested on all the specimens, and three multiplex kits, the RealCycler Universal ULCGEN (Progenie Molecular), the Allplex Genital Ulcer Assay (Seegene) and the VIASURE Haemophilus ducreyi + CT LGV Real Time PCR Detection kit (CerTest Biotec), tested on the 92 samples from symptomatic MSM. Clinical performance was determined in comparison to the in-house real time PCR targeting the pmpH and the ompA gene sequencing.ResultsOverall agreement ranged between 91.3% and 100% (95% CI 83.7–100%) with very good Kappa index values (>0.8). The clinical sensitivities and specificities varied between 91% and 100% (95% CI 80.8–100%), and 97% and 100% (95% CI 87.1–100%), respectively, with some kits performing better than others.DiscussionThe four assays showed very good performance for the detection of LGV on anorectal specimens.     

Comparison of chemiluminescent immunoassay and ELISA for measles IgG and IgM

In the context of measles elimination, the identification of recent infections is important for clinical laboratories. Serological diagnosis is achieved by detecting specific IgG and IgM. Recently an automated chemiluminescent immunoassay (CLIA) (Liaison, DiaSorin, Italy) has been used to quantify the measles antibody. The aim of this study was to compare this assay with Enzygnost ELISA (Siemens, Germany), with final classification of discrepancies by indirect immunofluorescence (Euroimmun, Germany). For measles IgM, 204 sera were analyzed: 50 IgM‐positive, 104 IgM‐negative/IgG‐positive, and 50 from other viral infections (B19V, rubella, mumps, CMV, and EBV). For the measles IgG assay, 162 samples were tested: 106 were positive and 56 were negative. For measles IgM, the sensitivity and specificity of CLIA against ELISA were 94% (95% CI: 83.2–98.6) and 100% (95% CI: 97.1–100), respectively; the corrected figures after the final classification of discrepancies were 100% (95% CI: 91.0–100) and 99.4% (95% CI: 96.1–100), respectively. In relation to IgG, the sensitivity and specificity of CLIA against ELISA were, respectively, 97.2% (95% CI: 91.7–99.4) and 92.9% (95% CI: 82.5–97.7), and 95.5% (95% CI: 89.5–98.3) and 100% (95% CI: 91.8–100) after the final classification. CLIA showed excellent sensitivity and specificity in detecting measles IgG and IgM antibodies, eliminating the need to aliquot specimens before carrying out the assay.     

Performance of a new rapid test for detecting anti-hepatitis E virus immunoglobulin M in immunocompetent and immunocompromised patients

BackgroundHepatitis E virus (HEV) infections are widespread in both developing and developed countries. It is, therefore, important to assess the performance of systems for rapidly detecting anti-HEV immunoglobulin M antibodies in human sera.ObjectivesTo evaluate the diagnostic value of a new immunochromatographic assay, the HEV IgM rapid test (Wantai).Study designBlood samples were taken from 30 acutely infected immunocompetent and 30 acutely infected immunocompromised patients, all with HEV RNA in their blood. Specificity and cross reactivity was assessed using samples from 30 HEV RNA negative immunocompetent patients who had acute Epstein–Barr virus (EBV) or cytomegalovirus (CMV) infections and 30 HEV RNA negative immunocompromised patients. The performance of the HEV IgM Rapid Test was compared to that of a conventional microplate enzyme immunoassay.ResultsThe sensitivity of the rapid test in immunocompetent patients was 90% (95% CI: 72.1–100%), similar to that of the Wantai microplate assay (sensitivity: 96.6%, 95% CI: 78.77–100%; p = 0.61). The sensitivity of the rapid test in immunocompromised patients was 73.3% (95% CI: 55.4–91.2%) and that of the microplate assay was 83.3% (95% CI: 65.44–100%; p = 0.53). The rapid test produced no false positive reactions with samples from HEV RNA negative patients; while the microplate assay gave two false positive results (3.3%).ConclusionThe new Wantai HEV IgM rapid test is easy to use and suitable for rapidly detecting acute hepatitis E infections in both immunocompetent and immunocompromised patients. However, HEV RNA must be detected using a molecular assay for diagnosing an HEV infection in anti-HEV IgM negative patients.     

Validation of a novel real-time PCR assay for detection of HLA-B*15:02 allele for prevention of carbamazepine – Induced Stevens-Johnson syndrome/Toxic Epidermal Necrolysis in individuals of Asian ancestry

ObjectivesScreening for the HLA-B*15:02 allele has been recommended to prevent carbamazepine (CBZ) – induced Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) in individuals with Asian ancestry. We aimed, therefore, to develop and validate a robust and inexpensive method for detection of the HLA-B*15:02 allele.MethodsReal-time PCR using TaqMan® probes followed by SYBR® Green was used to detect the HLA-B*15:02 allele prior to treatment with CBZ therapy.ResultsA total of 121 samples were tested. The assay has a sensitivity of 100% (95% CI: 76.84–100.0%), a specificity of 100% (95% CI: 96.61–100%), a positive predictive value of 100% (95% CI: 76.84–100%) and a negative predictive value of 100.0% (95% CI: 96.61–100.0%), respectively. There was 100% agreement between our results and genotyping using Luminex SSO/SBT/SSP. The lowest limit of detection of the TaqMan® probe is 0.05 ng/μl and the SYBR® Green is 0.5 ng/μl of DNA. The unit cost of using the TaqMan® probe followed by SYBR® Green is only $4.7 USD.ConclusionWe developed a novel assay for the detection of the HLA-B*15:02 allele, which is robust, inexpensive and suitable for screening individuals of Asian ancestry in the prevention of CBZ-induced SJS/TEN.     

Multisite Clinical Evaluation of a Rapid Test for Entamoeba histolytica in Stool

Rapid point-of-care detection of enteric protozoa in diarrheal stool is desirable in clinical and research settings to efficiently determine the etiology of diarrhea. We analyzed the ability of the third-generation E. histolytica Quik Chek assay developed by Techlab to detect amebic antigens in fecal samples collected from independent study populations in South Africa and Bangladesh. We compared the performance of this recently released rapid test to that of the commercially available ProSpecT Entamoeba histolytica microplate assay from Remel and the E. histolytica II enzyme-linked immunosorbent assay (ELISA) from Techlab, using real-time and nested-PCR for Entamoeba species to resolve any discrepant results. After discrepant resolution, The E. histolytica Quik Chek assay exhibited sensitivity and specificity compared to the E. histolytica II ELISA of 98.0% (95% confidence interval [CI], 92.9% to 99.8%) and 100% (95% CI, 99.0% to 100%), respectively. Compared to the ProSpecT microplate assay, the E. histolytica Quik Chek (Quik Chek) assay exhibited 97.0% sensitivity (95% CI, 91.5% to 99.4%) and 100% specificity (95% CI, 99.0% to 100%). Our results indicate that the Quik Chek is a robust assay for the specific detection of E. histolytica trophozoites in unfixed frozen clinical stool samples.     

Clinical and Analytical Performance of the Onclarity HPV Assay Using the VALGENT Framework

As the demand for human papillomavirus (HPV)-related cervical screening increases, emerging HPV tests must be evaluated robustly using well-annotated samples, such as those generated in the Validation of HPV Genotyping Tests (VALGENT) framework. Through VALGENT, we assessed the performance of the BD Onclarity HPV assay, which detects 14 high-risk (HR) types and resolves six individual types and three groups of types. Consecutive samples from a screening population (n = 1,000), enriched with cytologically abnormal samples (n = 300), that had been tested previously with the GP5+/6+ PCR enzyme immunoassay (EIA) and the GP5+/6+ PCR LMNX assay (Diassay) were tested with the Onclarity assay. Type-specific HPV prevalences were analyzed according to age and cytological result. The accuracy of the Onclarity assay for the detection of cervical intraepithelial neoplasia grade 2+ (CIN2+) and CIN3+ was assessed relative to the GP5+/6+ EIA results by using noninferiority criteria. Overall agreement and type-specific agreement between the Onclarity assay and the GP5+/6+ LMNX assay were assessed. The prevalence of HPV types 16, 18, 31, and 45 increased with the severity of cytological results (P for trend, <0.05). For the detection of CIN2+, the Onclarity assay had a relative sensitivity of 1.02 (95% confidence interval [CI], 0.99 to 1.05; P < 0.001 for noninferiority) and a relative specificity of 0.99 (95% CI, 0.97 to 1.00; P = 0.186 for noninferiority). The kappa for agreement between the Onclarity assay and the GP5+/6+ LMNX assay for HR-HPV was 0.92 (95% CI, 0.89 to 0.94), and values for the six individual types ranged from 0.78 (95% CI, 0.68 to 0.87) for HPV-52 to 0.96 (95% CI, 0.93 to 0.99) for HPV-16. These data suggest that the Onclarity assay offers applications for clinical workstreams while providing genotyping information that may be useful for risk stratification beyond types 16 and 18.     

Comparison of the Abbott RealTime High Risk HPV with Genomica HPV Clinical Array for the detection of human papillomavirus DNA

Human papillomavirus (HPV) has been identified as the major cause of cervical cancer worldwide and HPV DNA testing is recommended in primary cervical cancer screening. Several molecular tests for detection/typing of HPV DNA with different sensitivity and specificity are commercially available. The present study compared the performance of the Abbott RealTime High Risk HPV assay and the Genomica HPV Clinical Array CLART2 in 78 specimens (63 cervical smears and 15 rectal/urethral swabs).The typing results of the Genomica assay were in absolute agreement with each of the four possible result categories of the Abbott assay (HPV16, HPV18, Other HR HPV, not detected) in 87.2% (68/78) of the samples, with a Cohen' kappa agreement coefficient for every HR type of 0.62 (95% CI: 0.39–0.85), higher in cervical swabs (k = 0.74, 95% CI: 0.50–0.99) than in rectal/urethral swabs (k = 0.36, 95% CI: 0.00–0.82). There was an excellent agreement of the Genomica results with those of Abbott in cervical samples harbored HPV single infection (100% agreement). Nonetheless, both methods may lose sensitivity for detecting HPV types in multiple infections, giving discordant results (10/78). This underlines the importance of establishing the analytical sensitivity in HPV type detection in single and multiple HPV infections. In rectal/urethral swabs, 5 of 15 (33%) discordant cases were observed, most of which became compatible when the Genomica assay was performed starting from nucleic acid extracted with the Abbott m2000sp system. These results suggest that nucleic extraction based on the magnetic beads technique is suitable for HPV DNA detection in urethral/rectal swabs.     

Evaluation of the commercial AD fosfomycin test for susceptibility testing of multidrug-resistant Enterobacterales and Pseudomonas aeruginosa

ObjectivesTo compare fosfomycin susceptibility testing with the commercial agar dilution (AD) test, AD Fosfomycin (Liofilchem, Roseto degli Abruzzi, Italy) and the reference AD method, using a collection of multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa clinical isolates.MethodsThe collection included 119 carbapenemase-producing Enterobacterales, 53 Enterobacterales producing acquired AmpC-type and/or extended-spectrum β-lactamases and 38 carbapenemase-producing P. aeruginosa, including representatives of different high-risk clones. AD Fosfomycin and AD reference method (ISO 20776-1:2019) were performed starting from the same microbial suspension. Results were interpreted according to EUCAST clinical breakpoints (10.0). Essential agreement (EA), category agreement (CA) and error rates were calculated as described by the International Organization for Standardization.ResultsOf 172 Enterobacterales, 143 (83.1%, including 92.9% (52 of 56) of the NDM-producers and 84.2% (48 of 57) of the KPC-producers) were susceptible to fosfomycin using reference AD. A CA of 91.9% (158 of 172; 95% CI 87.1%–95.3%) and an EA of 92.5% (136 of 147; 95% CI 87.4%–96.0%), respectively, were calculated for the commercial AD Fosfomycin test, with 9.8% (14 of 143) of major errors and no very major errors (0 of 29). Overall, 86.8% (33 of 38) of P. aeruginosa showed a fosfomycin MIC ≤128 mg/L using reference AD. An EA of 84.8% (95% CI 66.3%–92.0%) was calculated for the commercial AD Fosfomycin test, with a CA of 100% (95% CI 93.6%–100%) when considering a tentative breakpoint at 128 mg/L.ConclusionsAD Fosfomycin showed an overall good concordance compared with reference AD.     

One-month humoral response following two or three doses of messenger RNA coronavirus disease 2019 vaccines as primary vaccination in specific populations in France: first results from the Agence Nationale Recherche contre le Sida (ANRS)0001S COV-POPART cohort

Objectives: We aimed to investigate the 1-month humoral response to two or three doses of a messenger RNA coronavirus disease 2019 (COVID-19) vaccine as a primary vaccination regimen in specific populations compared with that in healthy adults.MethodsAgence Nationale Recherche contre le Sida (ANRS)0001S–COV-POPART (NCT04824651) is a French nation-wide, multi-centre, prospective, observational cohort study assessing the immune response to COVID-19 vaccines routinely administered to 11 sub-groups of patients with chronic conditions and two control groups. Patients and controls who received at least two vaccine doses and whose results 1 month after the second dose were available were included. The humoral response was assessed 1 month after the first, second and third doses (if applicable) based on the percentage of responders (positive for anti-Spike severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] IgG antibodies), geometric means of anti-Spike SARS-CoV-2 IgG antibodies (enzyme-linked immunosorbent assay) and proportion of participants with anti-SARS-CoV-2-specific neutralizing antibodies (in vitro neutralization assay for the original SARS-CoV-2 strain). All analyses were centralized.ResultsWe included 4091 participants in this analysis: 2979 participants from specific sub-populations and 1112 controls. Only 522 (17.5%) participants from the specific populations received three doses as a primary vaccination regimen. Patients living with human immunodeficiency virus, cancer and diabetes had high percentages of responders after two doses, whereas patients with solid organ transplants, allogeneic hematopoietic stem cell transplants and hypogammaglobulinaemia had the lowest percentage of responders (35.9% [95% CI, 29.2–43.0], 57.4% [95% CI, 48.1–66.3] and 77.1% [95% CI, 65.6–86.3], respectively). In those who received the third dose, the percentage of responders reached 54.2% (95% CI, 42.9–65.2) (vs. 32.3% [95% CI, 16.7–51.4] after 2 doses) among those with solid organ transplants and 73.9% (95% CI, 58.9–85.7) (vs. 56.1% [95% CI, 46.2–65.7] after 2 doses) among those with hematopoietic stem cell transplants. Similar results were found with anti-SARS-CoV-2-specific neutralizing antibodies.ConclusionsA lower humoral response to COVID-19 vaccines was observed in the specific populations compared with that in the controls. The third dose of this vaccine in the primary regimen had a positive effect on the percentages of patients who developed anti-Spike IgG antibodies and specific neutralizing antibodies.     

Performance of a Novel Point-of-Care Molecular Assay for Detection of Influenza A and B Viruses and Respiratory Syncytial Virus (Enigma MiniLab) in Children with Acute Respiratory Infection

The performance of the Enigma MiniLab assay for influenza A and B viruses and respiratory syncytial virus (RSV) was compared to a centralized laboratory respiratory virus panel. The positive and negative percent agreement for influenza A virus, influenza B virus, and RSV were 79.2% (95% confidence interval [95% CI], 57.8 to 92.9%) and 99.4% (95% CI, 98.4 to 99.9), 100% (95% CI, 47.8 to 100%) and 100% (95% CI, 99.3 to 100%), 98.5% (95% CI, 94.6 to 99.8%) and 94.5% (95% CI, 91.9 to 96.4%), respectively.     

Antibodies to small ubiquitin-like modifier activating enzyme are associated with a diagnosis of dermatomyositis: results from an unselected cohort

The aim of this study was to examine the frequency and significance of antibodies targeting the small ubiquitin-like modifier 1 activating enzyme (SAE) in patients under serologic evaluation for idiopathic inflammatory myopathies. Patient sera (n?=?17) recognizing bands at approximately 40 (SAE1) and 90 (SAE2) kDa were identified in 6445 consecutive samples for myositis autoantibody evaluation by immunoprecipitation (IP) of S³⁵-labeled K562 cell lysate. All 17 positive samples, 176 disease, and 67 healthy controls were evaluated for SAE1 antibodies using a line immunoblot assay (LIA). Clinical data of SAE antibody-positive patients were obtained by retrospective chart review. Positivity with both methods was associated with a diagnosis dermatomyositis with characteristic skin manifestations of varying severity and muscle involvement. Majority of the patients were female (73.7%), mean age of 55.0 (range 12.0–82.0) years at the time of testing. Using the IP as reference, the SAE1 LIA had a sensitivity of 100% (95% CI 82.4–100%), specificity of 99.6% (95% CI 97.7–100%), positive predictive value of 95.0% (95% CI 75.1–99.9%), and negative predictive value of 100% (95% CI 98.5–100%). This study confirms the association of SAE antibodies in patients with dermatomyositis. A combination of IP and the LIA specific for SAE1 may be useful in antibody detection.     

Detection of Methicillin-Resistant Staphylococcus aureus by a Duplex Droplet Digital PCR Assay

Health care-associated infections with methicillin-resistant Staphylococcus aureus (MRSA) contribute to significant hospitalization costs. We report here a droplet digital PCR (ddPCR) assay, which is a next-generation emulsion-based endpoint PCR assay for high-precision MRSA analysis. Reference cultures of MRSA, methicillin-susceptible S. aureus (MSSA), and confounders were included as controls. Copan swabs were used to sample cultures and collect specimens for analysis from patients at a large teaching hospital. Swab extraction and cell lysis were accomplished using magnetic-driven agitation of silica beads. Quantitative PCR (qPCR) (Roche Light Cycler 480) and ddPCR (Bio-Rad QX100 droplet digital PCR system) assays were used to detect genes for the staphylococcal protein SA0140 (SA) and the methicillin resistance (mecA) gene employing standard TaqMan chemistries. Both qPCR and ddPCR assays correctly identified culture controls for MRSA (76), MSSA (12), and confounder organisms (36) with 100% sensitivity and specificity. Analysis of the clinical samples (211 negative and 186 positive) collected during a study of MRSA nasal carriage allowed direct comparison of the qPCR and ddPCR assays to the Cepheid MRSA GeneXpert assay. A total of 397 clinical samples were examined in this study. Cepheid MRSA GeneXpert values were used to define negative and positive samples. Both the qPCR and ddPCR assays were in good agreement with the reference assay. The sensitivities for the qPCR and ddPCR assays were 96.8% (95% confidence interval [CI], 93.1 to 98.5%) and 96.8% (95% CI, 93.1 to 98.5%), respectively. Both the qPCR and ddPCR assays had specificities of 91.9% (95% CI, 87.5 to 94.9%) for qPCR and 91.0% (95% CI, 86.4 to 94.2%) for ddPCR technology.     

Comparison of Established Diagnostic Methodologies and a Novel Bacterial smpB Real-Time PCR Assay for Specific Detection of Haemophilus influenzae Isolates Associated with Respiratory Tract Infections

Haemophilus influenzae is a significant causative agent of respiratory tract infections (RTI) worldwide. The development of a rapid H. influenzae diagnostic assay that would allow for the implementation of infection control measures and also improve antimicrobial stewardship for patients is required. A number of nucleic acid diagnostics approaches that detect H. influenzae in RTIs have been described in the literature; however, there are reported specificity and sensitivity limitations for these assays. In this study, a novel real-time PCR diagnostic assay targeting the smpB gene was designed to detect all serogroups of H. influenzae. The assay was validated using a panel of well-characterized Haemophilus spp. Subsequently, 44 Haemophilus clinical isolates were collected, and 36 isolates were identified as H. influenzae using a gold standard methodology that combined the results of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) and a fucK diagnostic assay. Using the novel smpB diagnostic assay, 100% concordance was observed with the gold standard, demonstrating a sensitivity of 100% (95% confidence interval [CI], 90.26% to 100.00%) and a specificity of 100% (95% CI, 63.06% to 100.00%) when used on clinical isolates. To demonstrate the clinical utility of the diagnostic assay presented, a panel of lower RTI samples (n = 98) were blindly tested with the gold standard and smpB diagnostic assays. The results generated were concordant for 94/98 samples tested, demonstrating a sensitivity of 90.91% (95% CI, 78.33% to 97.47%) and a specificity of 100% (95% CI, 93.40% to 100.00%) for the novel smpB assay when used directly on respiratory specimens.