Duplex nucleic acid test for the detection of chikungunya and dengue RNA viruses in blood donations.

BACKGROUND: Chikungunya (CHIKV) and dengue (DENV) viruses are primarily mosquito-borne, but transfusion transmission can occur (DENV) or is likely (CHIKV). In the absence of commercially available blood screening assays, a variety of strategies to ensure recipient safety in the face of expanding CHIKV and/or DENV outbreaks have been used. STUDY DESIGN AND METHODS: Performance of cobas CHIKV/DENV, a qualitative RNA detection assay for use on the cobas 6800/8800 Systems, was evaluated at two sites (Roche Molecular Systems, Inc. [RMS], and the American Red Cross [ARC]). Analytical sensitivity, genotype inclusion, correlation with other assays, and reproducibility used clinical CHIKV- or DENV-positive samples and secondary standards for DENV Types 1 to 4 and for three CHIKV genotypes (Asian; East Central South African; and West African); each secondary standard was traceable to international reference panels or reagents. Evaluation of analytic specificity assessed other microorganisms for interference and cross-reactivity; clinical specificity was determined by individually testing 10,528 volunteer blood donations from the continental United States. RESULTS: The 50 and 95% limit of detection (LoD) obtained by RMS for CHIKV, Asian genotype was 1.8 and 6.8 Detectable Units (DU)/mL, respectively, and 0.14 and 0.63 International Units (IU)/mL, respectively for DENV-1. No significant differences in detection occurred by testing at a second site, the ARC (2.4 and 10.5 DU/mL for CHIKV and 0.15 and 0.60 IU/mL for DENV). Clinical specificity was 100% (95% confidence interval, 99.965%-100%) for CHIKV and DENV. CONCLUSIONS: The high sensitivity and specificity of the cobas CHIKV/DENV test, as demonstrated in these evaluations, indicate its suitability for blood donation screening.

Evaluation of a new West Nile virus nucleic acid test for screening of blood donations.

BACKGROUND: West Nile virus (WNV) is transmitted to humans through mosquito bites and can be further transmitted to humans through transfusion or transplantation. Because most infected individuals are asymptomatic, blood donor screening is important in areas where WNV is endemic. These studies evaluated the performance of a new test for detection of WNV RNA in blood donations. STUDY DESIGN AND METHODS: Analytical performance evaluation included sensitivity, specificity, inclusivity, and correlation. A clinical specificity study was conducted at four blood donor testing laboratories in parallel with the cobas TaqScreen WNV Test (Roche Molecular Systems, Inc.). RESULTS: The 95% and 50% limit of detection for cobas WNV was 12.9 copies/mL (95% confidence interval [CI], 10.8-16.3) and 2.1 copies/mL (95% CI, 1.9-2.4) for WNV lineage 1, respectively, and 6.2 copies/mL (95% CI, 4.8-8.9) and 1.1 copies/mL (95% CI, 0.8-1.3) for WNV lineage 2, respectively. Clinical specificity was 100% in 10,823 donor samples tested individually (95% CI, 99.966%-100%) and 63,243 tested in pools of 6 (95% CI, 99.994%-100%). Samples of other members of the Japanese encephalitis virus serocomplex, including St Louis encephalitis, Japanese encephalitis, Murray Valley encephalitis, Usutu, and Kunjin viruses were detected by cobas WNV. CONCLUSION: The cobas WNV test for use on the cobas 6800/8800 System, a fully automated test system, demonstrated high sensitivity and specificity and is suitable for the detection of WNV in blood donors.

Sensitivity and specificity of a new automated system for the detection of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus nucleic acid in blood and plasma donations.

BACKGROUND: Use of nucleic acid testing (NAT) in donor infectious disease screening improves transfusion safety. Advances in NAT technology include improvements in assay sensitivity and system automation, and real-time viral target discrimination in multiplex assays. This article describes the sensitivity and specificity of cobas MPX, a multiplex assay for detection of human immunodeficiency virus (HIV)-1 Group M, HIV-2 and HIV-1 Group O RNA, HCV RNA, and HBV DNA, for use on the cobas 6800/8800 Systems. STUDY DESIGN AND METHODS: The specificity of cobas MPX was evaluated in samples from donors of blood and source plasma in the United States. Analytic sensitivity was determined with reference standards. Infectious window periods (WPs) before NAT detectability were calculated for current donor screening assays. RESULTS: The specificity of cobas MPX was 99.946% (99.883%-99.980%) in 11,203 blood donor samples tested individually (IDT), 100% (99.994%-100%) in 63,012 donor samples tested in pools of 6, and 99.994% (99.988%-99.998%) in 108,306 source plasma donations tested in pools of 96. Seven HCV NAT-yield donations and one seronegative occult HBV infection were detected. Ninety-five percent and 50% detection limits in plasma (IU/mL) were 25.7 and 3.8 for HIV-1M, 7.0 and 1.3 for HCV, and 1.4 and 0.3 for HBV. The HBV WP was 1 to 4 days shorter than other donor screening assays by IDT. CONCLUSION: cobas MPX demonstrated high specificity in blood and source plasma donations tested individually and in pools. High sensitivity, in particular for HBV, shortens the WP and may enhance detection of occult HBV.

Does melatonin improve sleep in older people? A randomised crossover trial.

STUDY OBJECTIVE: to determine whether melatonin will improve quality of sleep in healthy older people with age-related sleep maintenance problems. DESIGN: a double blind randomised placebo controlled crossover trial in healthy older volunteers. SETTING: a largely urban population, Auckland, New Zealand. PARTICIPANTS: participants were part of the larger Possible Role of Melatonin in Sleep of Elders study. People 65 years or more of age were recruited through widespread advertising. We screened 414 potential participants by mail using the Pittsburgh Sleep Quality Index, and selected 194 for clinic interview. Exclusions included depression, cognitive impairment, hypnosedative medications, sleep phase abnormalities, medical and/or environmental problems that might impair sleep. Twenty normal and 20 problem sleepers were randomly allocated for this study from a larger sample of 60 normal and 60 problem sleepers. MEASUREMENTS AND RESULTS: 24-hour urine 6-sulphatoxymelatonin was measured to estimate melatonin secretion in each participant. Five milligrams of melatonin, or matching placebo were each taken at bedtime for 4 weeks, separated by a 4-week washout period. Sleep quality was measured using sleep diaries, the Leeds Sleep Evaluation Questionnaire, and actigraphy. There was a significant difference between the groups in self-reported sleep quality indicators at entry, but no difference in melatonin secretion. Melatonin did not significantly improve any sleep parameter measured in either group. CONCLUSION: 5 mg of fast release melatonin taken at bedtime does not improve the quality of sleep in older people with age-related sleep maintenance problems.