Comparison Of Viral Load Assays

A number of studies have compared the performance of these assays in clinical situations. Schuurman et al.[4] showed that interlaboratory reproducibility of the Roche, Organon, and Versant assays was very good. Others have shown that each of the assays has relatively low intra- and interassay variability.1-5-1 The biological variation of HIV-1 RNA in plasma in clinically stable individuals is approximately threefold (0.5 log) and this variation was not associated with diurnal fluctuations.1-6-1 The anticoagulant used is important for optimal results and the preferred anticoagulant for bDNA is EDTA while citrate or EDTA may be used for NASBA and RT-PCR. Heparin interferes with reagents used in the assays and should be avoided and there is also some question over its effectiveness as a preservative for RNA.

Some samples give discrepant results between assay systems and therefore the assays should not be used interchangeably.1-7-1 Of concern is that all commercially available kit-based assays have been optimized against HIV-1 clade B viruses which predominate in North America and Europe but represent only 3% of infections worldwide.[8,9] The challenge for commercial nucleic acid-based tests is to detect and quantify accurately very divergent strains of HIV-1 and HIV-2. Under detection or complete lack of detection of some strains of HIV remains a major concern.[8,10] Recombination between distantly related strains may further contribute to the emergence of HIV-1 viral variants that escape detection or are under-detected by current molecular tests and there are several circulating recombinant forms or CRFs which may contain sequences from more than one strain of HIV-1. Comparison of the performance of bDNA and RT-PCR assays for the quantification of viral load from patients infected with non-clade B strains of HIV-1 has shown greater than 1.0

log variation in the detection of some strains.[10] The choice of method for quantification is dictated by throughput of samples and the genetic makeup of the patient cohort. There is an urgent requirement for international standards which should include non-clade B strains to enable quality control of viral load measurements.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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