Comparison of PneumID real-time PCR assay with Amplex eazyplex LAMP assay for laboratory diagnosis of Pneumocystis jirovecii Pneumonia.

We compared PneumID PCR with Amplex eazyplex LAMP assay for the diagnosis of Pneumocystis jirovecii pneumonia (PJP). Both assays enable accurate diagnosis of definite PJP. Cut-off cycle threshold of the PneumID assay was < 26.68 while the cut-off time-to-positivity of the eazyplex assay was 16:02 (minutes:seconds). The positive and negative percentage agreement of eazyplex assay with PneumID assay was 75.0% and 100.0% respectively, while the overall agreement was substantial with kappa = 0.80. For both assays, establishment of cut-off values to differentiate probable PJP from colonization was not feasible as results overlapped.

Both PneumID PCR and Amplex eazyplex LAMP assay enable accurate diagnosis of definite Pneumocystis jirovecii pneumonia (PJP). PneumID assay was more sensitive than eazyplex assay for detection of P. jirovecii. However, differentiation between probable PJP from colonization was not feasible.

Rapid adaptation and continuous performance evaluation of SARS-CoV-2 envelope gene (E-gene) real-time RT-PCR assays to support the hospital surge in test demand.

We describe the timely adaption of both published WHO E-gene protocol and commercially available LightMix Modular E-gene assay to the test platform (ABI 7900 Fast real-time analyzer and TaqMan Fast One-step Virus Master Mix) available in an accredited tertiary hospital laboratory with an on-going evaluation to ensure the provision of quality service within the time constraint. The LightMix Modular E-gene was slightly more sensitive when compared to the WHO E-gene, both analytically and diagnostically. The assay was recommended for screening of SARS-CoV-2 infection. With the availability of technically competent staff through continuous training, the provision of round-the-clock service is feasible despite the test is of high complexity. The thermal cycling duration of the adapted LightMix E-gene and WHO E-gene is shortened by half and one hour respectively and allows the number of runs to double when 24-h round-the-clock service is provided. An increase in testing capacity could support surges in testing demand, which is essential to control the current SARS-CoV-2 pandemic, to prevent potential overwhelming of the healthcare system, and to optimize utilization of the isolation beds.

Hepatitis B infection acquired after haematopioetic stem cell transplant through horizontal mode.

A 22 month old child with thalassaemia major received unrelated umbilical cord blood transplantation. She was born to mother of HBsAg carrier and received hepatitis B immunoglobulin at birth and hepatitis B vaccination. She was HBsAg negative and anti-HBs positive before transplantation. After transplant, she was taken care by her mother and found to be HBsAg positive at 2 year post-transplant. Genotyping of the mother's and child's HBV status confirmed to be of same genotype and demonstrated horizontal transmission in post-transplant setting. Passive immunization of HBV may be considered in early post-transplant phase to prevent horizontal transmission of HBV, and antiviral treatment of the carer should be offered to prevent transmission of infection to immunocompromised child.

Virulence potential of fusogenic orthoreoviruses.

Several severe respiratory virus infections that have emerged during the past decade originated in animals, including bats. In Indonesia, exposure to bats has been associated with increased risk of acquiring orthoreovirus infection. Although orthoreovirus infections are mild and self-limiting, we explored their potential for evolution into a more virulent form. We used conventional virus culture, electron microscopy, and molecular sequencing to isolate and identify orthoreoviruses from 3 patients in whom respiratory tract infection developed after travel to Indonesia. Virus characterization by plaque-reduction neutralization testing showed antigenic similarity, but sequencing of the small segment genes suggested virus reassortment, which could lead to increased virulence. Bats as a reservoir might contribute to virus evolution and genetic diversity, giving orthoreoviruses the potential to become more virulent. Evolution of this virus should be closely monitored so that prevention and control measures can be taken should it become more virulent.

Coxsackievirus B3-associated aseptic meningitis: an emerging infection in Hong Kong.

Enterovirus (EV) infection is a common disease of childhood and associated not uncommonly with aseptic meningitis. In the summer of 2008, laboratory surveillance has detected increased number of coxsackievirus B3 (CVB3) associated aseptic meningitis in Hong Kong, constituting 11.6% of those infected. This study analyzed the epidemiology, circulating pattern, and clinical presentations of CVB3 in Hong Kong over the last 10 years with reference to the circulation of EV in the locality. Enteroviruses (EV) were isolated from respiratory, cerebrospinal fluid (CSF), stool, and vesicular samples using human rhabdomyosarcoma, human laryngeal carcinoma (HEp2-C), human lung fibroblast (MRC-5), and African green monkey kidney (Vero) cell lines. Virus isolates were identified and characterized by indirect immunofluorescence (IF) using monoclonal antibodies (mAB), neutralization test as well as partial VP1 sequencing. Different from previous years, IF test result showed that majority of the isolates from 2008 were untypeable by the mAB suggesting antigenic change. Sequence analysis revealed that these isolates were clustered with recent isolate from Fuyang, China. Review of data from 1999 to 2008 showed increased activity of CVB3 in the years 2005 and 2008, and isolates in these 2 years displayed an amino acid change from threonine to alanine at codon 277 of the VP1 gene, which may be associated with central nervous system (CNS) disease.

Sero-immunity and serologic response to pandemic influenza A (H1N1) 2009 virus in Hong Kong.

To study the serologic response to the new pandemic influenza A (H1N1) 2009 virus in Hong Kong, the level of immunity was measured before and after the occurrence of the outbreak, and the titer of antibody to the pandemic influenza A (H1N1) 2009 virus in serum samples of laboratory confirmed cases. The presence of pre-outbreak pandemic influenza A (H1N1) 2009 virus antibodies in 37% of individuals older than >65 years suggested previous exposures to heterologous virus strains may have elicited cross-reacting antibody. Following large outbreaks of pandemic influenza A 2009 virus that peaked in September 2009, there is a change in immunity level in various age groups consistent with the attack rates among population in Hong Kong. Among individuals with mild clinical presentation, the antibody response to pandemic influenza A (H1N1) 2009 virus was stronger in those individuals aged ≤ 24 years but took more time to reach a titer of 40 when compared with those aged >24 years; however, the antibody level declined slower among individuals aged ≤ 24 years. Regardless of age, the antibody response rose rapidly and reached much higher titer among individuals with severe clinical presentation. Further study is required to collect additional data on antibody persistence and determine how much protection is conferred by previous exposure to seasonal influenza A (H1N1) viruses.

Comparison of laboratory diagnostic methods for measles infection and identification of measles virus genotypes in Hong Kong.

The sensitivities of IgM detection, virus isolation, and RT-PCR for the diagnosis of measles infection were assessed using samples collected from confirmed measles cases from 2006 to 2009. The optimal timing of specimen collection and the preferred specimen type(s) for these tests were also determined. IgM detection showed highest sensitivity when serum samples were collected >or=5 days after rash onset. Virus isolation gave the highest sensitivity when samples were collected

Comparison of CaptiaTM Measles IgG Assay with Vidas® Measles IgG Assay for determination of immune protection status against measles virus.

BACKGROUND: Correlation of the assay cut-off values for CaptiaTM Measles IgG and the Vidas® Measles IgG assays with the World Health Organization recommended immunoprotective level of ≥120 mIU/mL is not stated by the manufacturers. Lack of such information may affect interpretation of immune protection (IP) for measles. OBJECTIVE: The aim of this study was to compare the relative performance of the CaptiaTM Measles IgG assay and the Vidas® Measles IgG assay for determination of IP against measles virus. STUDY DESIGN: Correlation of the cut-off value of both assays with the immunoprotective level was determined with the 3rd WHO Measles IgG International Standard. One hundred clinical samples including frozen and fresh were tested with both assays. The positive percentage agreement (PPA) based on the manufacturers' interpretation and the WHO recommended immunoprotective level was compared. RESULTS: Samples tested positive by the CaptiaTM assay were at or above the immunoprotective level while those tested equivocal and positive by the Vidas® assay were immune protective. The overall PPA between both assays was 78.31 % (95 % CI = 67.91-86.61%). When Vidas® equivocal results were regarded as immunoprotective, the overall IP agreement was 96.39 % (95 % CI = 89.80-99.25 %). CONCLUSIONS: CaptiaTM assay was more sensitive than the Vidas® assay in determination of IP against measles virus. Testing of measles immunity with the Vidas® Measles IgG assay might underestimate the IP unless equivocal results were regarded as immunoprotective.

Performance evaluation of the re-standardized Abbott Architect anti-HBs assay.

BACKGROUND: As defined by World Health Organization (WHO), an antibody level of ≥ 10mIU/mL to hepatitis B virus confers protection. With the launching of Abbott anti-HBs assay re-standardized to the 2nd WHO International Reference Preparation, a positive bias in antibody level would be anticipated. Manufacturer provides limited data for samples around the immune cut-off which has potential implication on vaccine guidance. OBJECTIVES: To evaluate the performance of the re-standardized Abbott Architect anti-HBs assay and to determine the impact of the upward shift. STUDY DESIGN: A total of 52 samples, including 12 external quality assurance programme samples and 40 clinical samples were tested with both the Abbott 1st WHO standardized and the 2nd WHO re-standardized assay and results compared. The 2nd WHO anti-HBs standard and Acometrix anti-HBs control were also included for comparison. RESULTS: Verification of the re-standardized assay with the 2nd WHO anti-HBs standard revealed positive bias with mean closer to target value. Overall, the positive bias introduced by the new assay will only affect interpretation of samples with anti-HBs levels > 5.00 to < 10.00 mIU/mL previously tested on the Abbott 1st WHO standardized anti-HBs assay. CONCLUSIONS: Final interpretation of immune status to hepatitis B was not affected by the upward shift following introduction of the new Abbott anti-HBs assay except for previously negative samples with anti-HBs levels between >5.00 to <10.00 mIU/mL.

Comparison of the Cepheid Xpert Xpress Flu/RSV Assay to in-house Flu/RSV triplex real-time RT-PCR for rapid molecular detection of Influenza A, Influenza B and Respiratory Syncytial Virus in respiratory specimens.

This study compared the performance of the commercially available Xpert Xpress Flu/RSV assay to an in-house FluAB/RSV triplex real-time RT-PCR assay for the detection of influenza A/B viruses and respiratory syncitial virus (RSV) from both nasopharyngeal aspirate (NPA) and nasopharyngeal flocked swab (NPS). A total of 20 external quality assurance (EQA) samples and 172 clinical respiratory samples were tested prospectively using both the Xpert Xpress Flu/RSV assay and the in-house FluAB/RSV triplex assay. For the EQA samples, concordance rate was 100 % when tested with both assays. For clinical samples, there was 100 % agreement between the two assays for detection of influenza A and influenza B, 96.7 % agreement for detection of RSV and 99.7 % agreement for negative results. With a shortened turnaround time and good diagnostic performance, application of the Xpert Xpress Flu/RSV assay can facilitate patient triage for prompt implementation of infection control measures and management of high-risk patients during influenza epidemics.

The impact of pandemic influenza A (H1N1) 2009 on the circulation of respiratory viruses 2009-2011.

Surveillance of respiratory viruses has been conducted for many years at the public health laboratory in Hong Kong. With the occurrence of pandemic influenza A (H1N1) 2009, we observed a change in the seasonality of influenza activity with a seemingly corresponding change in the activity of respiratory syncytial virus, parainfluenza virus, and adenovirus during 2009-2011. This phenomenon could most likely be explained by virus interference.

Performance of laboratory diagnostics for the detection of influenza A(H1N1)v virus as correlated with the time after symptom onset and viral load.

BACKGROUND: To diagnose influenza A(H1N1)v virus infection, accurate and rapid detection are important. However, there is scanty data on the performance of various laboratory diagnostics. OBJECTIVE: To compare the performance of rapid antigen test (RAT), viral culture and RT-PCR for the detection of influenza A(H1N1)v virus and to correlate their performance with the time after symptom onset and viral load. STUDY DESIGN: From May 1, 2009 to June 25, 2009, respiratory samples were collected from 5740 individuals suspected of having influenza A(H1N1)v infection. The performance of viral culture and RT-PCR were investigated and correlated with the time after symptom onset. The sensitivity of RAT ESPLINE influenza A & B-N (Fujirebio Inc, Tokyo) was evaluated using a subset of 60 samples from patients diagnosed as having influenza A(H1N1)v infection. RESULTS: Using respiratory samples from 587 patients diagnosed with influenza A(H1N1)v infection, comparison of laboratory diagnostics showed viral culture and RT-PCR gave comparable results with overall sensitivity of 93.9% and 98.1%, respectively. For RAT, when testing a subset of 60 samples collected < or =3 days following symptom onset, the sensitivity was 62%. CONCLUSIONS: Although viral shedding is prolonged and of higher titre in influenza A(H1N1)v infection, RAT showed a low sensitivity of 62% among patients presenting < or =3 days after symptom onset. Viral culture showed comparable performance with RT-PCR and with sensitivity better than that documented for seasonal influenza.

Atypical norovirus epidemic in Hong Kong during summer of 2006 caused by a new genogroup II/4 variant.

An atypically high level of norovirus activity was noticed in Hong Kong beginning in early May 2006. A study was carried out to investigate whether this was caused by a new norovirus variant. Epidemiological data including monthly positivity rates and the numbers of outbreaks per month from January to July 2006 were analyzed and compared to those from 2002 to 2005. In a comparison with the epidemiological data from 2001 to 2005, an atypical peak of norovirus-associated gastroenteritis outbreak was observed beginning in May 2006, concurring with a striking increase in norovirus activity. Most of the outbreaks (>60%) were located in homes for the elderly. Phylogenetic analysis for both RdRp and 5' capsid regions showed that this epidemic was caused by a new genogroup II/4 variant. This variant was genetically distinct from the predominant variants of 2002 and 2004 but was closely related to one of the 95/96-subset variants which caused an epidemic in Hong Kong in 2001, suggesting that the 95/96 subset may be starting to recirculate.