Calibration of qualitative HBsAg assay results for quantitative HBsAg monitoring.

Evidence is accumulating that quantitative hepatitis B surface antigen monitoring may be useful in managing patients with chronic HBV infection on certain treatment regimens. Based on these results with the Abbott Architect qualitative and quantitative HBsAg assays, it seems feasible to convert qualitative to quantitative HBsAg values for this purpose.

Discrepant HIV results resolved by human DNA testing.

A high-risk patient was informed of a positive HIV antibody/antigen test. However, follow-up samples taken 2-3 months later for HIV RNA and anti-HIV antibodies were negative. Human DNA testing confirmed that all samples were from this patient, excluding a sample mix-up. Laboratory investigations revealed a likely splash-over contamination event.

The need for a sequencing-based assay to supplement the Abbott m2000 RealTime HCV Genotype II assay: a 1 year analysis.

BACKGROUND: Hepatitis C (HCV) genotyping is important for treatment planning. The Abbott m2000 RealTime HCV Genotype II assay is a PCR-based assay targeting specific regions of the 5'NCR gene for genotypes 1-6, and the NS5b gene for subgenotypes 1a/1b. However, not all genotypes can be resolved, with results being reported as: 'indeterminate', 'mixed', 'genotype X reactivity with Y', or just the major genotype 1 alone. OBJECTIVES AND STUDY DESIGN: To assess the supplementary testing required for these unresolved HCV genotypes, these samples were tested further using an in-house core/E1 sequencing assay. The resulting genotypes/subgenotypes were assigned using phylogenetic analysis with reference HCV genotype sequences. Additional testing was conducted using the INNO-LiPA HCV II assay for truly mixed genotypes. RESULTS: Out of 1052 samples tested, 89 (8.5%) underwent further sequencing to determine the HCV genotype: 16 that were 'indeterminate' on the m2000, were mostly genotype 2s and 3s by sequencing; 12 that were 'mixed', were mostly one of the genotypes reported in the mixture; 7 that were 'X reactivity with Y', were usually genotype X; 54 that gave just a major genotype 1 result were mostly 1a, with some 6 and 1b, and a few 1c. For three truly mixed genotypes, additional testing using the VERSANT(®) HCV Genotype Assay (LiPA) 2.0, showed two mixed 1 and 3, and one indistinguishable 6c-6l genotypes. CONCLUSIONS: The Abbott m2000 RealTime HCV Genotype II assay can resolve most (∼90%) HCV genotypes. However in 9-10% of cases, to fully resolve the genotype, additional testing is required.

Sensitivity of rapid influenza diagnostic testing for swine-origin 2009 a (H1N1) influenza virus in children.

BACKGROUND: The rapidly evolving pandemic of novel 2009 swine-origin influenza A (H1N1) virus (S-OIV) demands that accurate and practical diagnostics be urgently evaluated for their potential clinical utility. OBJECTIVE: To determine the diagnostic accuracy of a rapid influenza diagnostic test (RIDT) and direct fluorescent antibody (DFA) assay for S-OIV by using reverse-transcription polymerase chain reaction (RT-PCR) as the reference standard. METHODS: We prospectively recruited children (aged 0-17 years) assessed in the emergency department of a pediatric referral hospital and a community pediatric clinic for influenza-like illness between May 22 and July 25, 2009. RIDT (performed on-site) and DFA were compared with RT-PCR to determine their sensitivity and specificity for S-OIV. We also compared the sensitivity of RIDT for S-OIV to that for seasonal influenza over 2 preceding seasons. RESULTS: Of 820 children enrolled, 651 were from the emergency department and 169 were from the clinic. RIDT sensitivity was 62% (95% confidence interval [CI]: 52%-70%) for S-OIV, with a specificity of 99% (95% CI: 92%-100%). DFA sensitivity was 83% (95% CI: 75%-89%) and was superior to that of RIDT (P < .001). RIDT sensitivity for S-OIV was comparable to that for seasonal influenza when using DFA supplemented with culture as the reference standard. RIDT sensitivity for influenza viruses was significantly higher in children 5 years of age or younger (P = .003) and in patients presenting < or =2 days after symptom onset (P < .001). CONCLUSIONS: The sensitivity of RIDT for detection of S-OIV is higher than recently reported in mixed adult-pediatric populations but remains suboptimal.

Comparison of human metapneumovirus infection with respiratory syncytial virus infection in children.

We aimed to validate a direct immunofluorescence assay (DFA) for the detection of human metapneumovirus (hMPV) from nasal swabs and to determine the incidence and clinical features of this viral infection in a pediatric population. One hundred twenty-one of 3026 nasal swabs were positive for hMPV by DFA (4.0%). Compared with reverse transcriptase polymerase chain reaction, the sensitivity and specificity of DFA were 90%, and 100%, respectively. Compared with RSV, hMPV infection was more common in children with congenital abnormalities, particularly those with cardio-pulmonary dysplasia and was associated with an increased ventilatory requirement.

The complete sequence of a human parainfluenzavirus 4 genome.

Although the human parainfluenza virus 4 (HPIV4) has been known for a long time, its genome, alone among the human paramyxoviruses, has not been completely sequenced to date. In this study we obtained the first complete genomic sequence of HPIV4 from a clinical isolate named SKPIV4 obtained at the Hospital for Sick Children in Toronto (Ontario, Canada). The coding regions for the N, P/V, M, F and HN proteins show very high identities (95% to 97%) with previously available partial sequences for HPIV4B. The sequence for the L protein and the non-coding regions represent new information. A surprising feature of the genome is its length, more than 17 kb, making it the longest genome within the genus Rubulavirus, although the length is well within the known range of 15 kb to 19 kb for the subfamily Paramyxovirinae. The availability of a complete genomic sequence will facilitate investigations on a respiratory virus that is still not completely characterized.

Identification of severe acute respiratory syndrome in Canada.

BACKGROUND: Severe acute respiratory syndrome (SARS) is a condition of unknown cause that has recently been recognized in patients in Asia, North America, and Europe. This report summarizes the initial epidemiologic findings, clinical description, and diagnostic findings that followed the identification of SARS in Canada. METHODS: SARS was first identified in Canada in early March 2003. We collected epidemiologic, clinical, and diagnostic data from each of the first 10 cases prospectively as they were identified. Specimens from all cases were sent to local, provincial, national, and international laboratories for studies to identify an etiologic agent. RESULTS: The patients ranged from 24 to 78 years old; 60 percent were men. Transmission occurred only after close contact. The most common presenting symptoms were fever (in 100 percent of cases) and malaise (in 70 percent), followed by nonproductive cough (in 100 percent) and dyspnea (in 80 percent) associated with infiltrates on chest radiography (in 100 percent). Lymphopenia (in 89 percent of those for whom data were available), elevated lactate dehydrogenase levels (in 80 percent), elevated aspartate aminotransferase levels (in 78 percent), and elevated creatinine kinase levels (in 56 percent) were common. Empirical therapy most commonly included antibiotics, oseltamivir, and intravenous ribavirin. Mechanical ventilation was required in five patients. Three patients died, and five have had clinical improvement. The results of laboratory investigations were negative or not clinically significant except for the amplification of human metapneumovirus from respiratory specimens from five of nine patients and the isolation and amplification of a novel coronavirus from five of nine patients. In four cases both pathogens were isolated. CONCLUSIONS: SARS is a condition associated with substantial morbidity and mortality. It appears to be of viral origin, with patterns suggesting droplet or contact transmission. The role of human metapneumovirus, a novel coronavirus, or both requires further investigation.