Prevalence of canine intestinal parasites identified through quantitative sucrose flotation and immunofluorescent assay.

*<p>Overall prevalence was calculated as the number of samples with at least one parasite type divided by the total sample number.</p

Results of serological analyses and criteria for sero-status in people.

<p>Results of serological analyses and criteria for sero-status in people.</p

Technical and Regulatory Shortcomings of the TaqMan Version 1 HIV Viral Load Assay

<div><h3>Background</h3><p>The lower limit of detection of the original Roche Amplicor HIV plasma viral load (pVL) assay (50 copies/mL) has defined HIV treatment success. The Amplicor assay, however, has been replaced by the Roche TaqMan assay(s). Changes to the limits of detection and calibration have not been validated for clinical utility. Sudden increases in the number of patients with detectable pVL have been reported following the introduction of the TaqMan version 1 assay.</p> <h3>Methods</h3><p>Between October 2009 and April 2010 all routine pVL samples from British Columbia, Canada, with 40–250 copies/mL by TaqMan were re-tested by Amplicor (N = 1198). Subsequent short-term virological and resistance outcomes were followed in patients with unchanged therapy (N = 279; median 3.2 months follow-up).</p> <h3>Results</h3><p>TaqMan and Amplicor values correlated poorly at low pVL values. Low-level pVL by TaqMan was not associated with impending short-term virological failure; only 17% of patients with 40–250 copies/mL by TaqMan had detectable pVL by Amplicor at follow-up. During the follow-up period only 20% of patients had an increase in pVL by TaqMan (median [IQR]: 80 [36–283] copies/mL). In addition, in ∼2.4% of samples pVL was dramatically <em>underestimated</em> by TaqMan due to poor binding of the proprietary TaqMan primers.</p> <h3>Conclusions</h3><p>The replacement of Amplicor with the TaqMan assay has altered the previously accepted definition of HIV treatment failure without any evidence to support the clinical relevance of the new definition. Given the systematic differences in measurement in the low pVL range the British Columbia HIV treatment guidelines now use a threshold of >250 copies/mL by TaqMan to define treatment failure.</p> </div

Systematic underestimation of plasma viral load by TaqMan v1 in a minority of patients.

<p>A minority (2.4%) of samples had viral loads <i>underestimated</i> by >0.5 log₁₀ copies/mL by TaqMan v1 after re-testing with Amplicor v1.5. Depicted here is the viral load history of one representative patient showing systematic underestimation of viral load by TaqMan v1 when compared to results obtained by re-testing samples with the Amplicor v1.5, TaqMan v2 and/or Abbott assays. TaqMan v1 viral load results are shown as solid triangles (▴) joined by a solid line. Overlaid are the corresponding results from the Amplicor v1.5 (solid squares ▪), TaqMan version 2 (unshaded triangles Δ) and Abbott (unshaded squares γ) assays where available. For this patient TaqMan v1 systematically under-reported pVL by an average of 1.3 log₁₀ copies/mL over a period of 18 months.</p

Plasma viral load testing and reporting protocol in British Columbia between October 2009 and April 2010.

<p>All plasma samples were initially tested with the Roche COBAS AmpliPrep/COBAS TaqMan v1 HIV-1 Test (“TaqMan v1”) assay. TaqMan v1 pVL results <40 or ≥250 copies/mL were reported to physicians. Samples with TaqMan v1 pVL ≥40 and <250 copies/mL were re-tested by the Roche COBAS AmpliPrep/COBAS AMPLICOR HIV-1 MONITOR UltraSensitive Test, version 1.5 (“Amplicor v1.5”). The Amplicor v1.5 test results were reported to physicians.</p

Low-level viremia by TaqMan v1 does not predict short-term virological failure.

<p>A subset of patients (N = 279) with low-level viremia (40–250 copies/mL) by TaqMan v1 were followed longitudinally for a median of 3.2 months (IQR: 2.0–4.2 months). Patients initiated HAART at least 6 months prior, and treatment regimens remained unchanged over the course of follow-up. Samples from patients' latest follow-up visit were re-tested with the TaqMan v1 and Amplicor v1.5 assays. Overall 17% of patients had a detectable viral load by Amplicor v1.5 at their latest follow-up visit, while 38% were detectable by TaqMan v1. When patients were grouped according to their baseline TaqMan v1 pVL into 50 copies/mL strata we observed a stepwise increase in the proportion of patients with detectable pVL at their latest follow-up visit by both Amplicor v1.5 (red bars) and TaqMan v1 (blue bars). Consistent with previous results, more patients had detectable pVL by TaqMan v1 than by Amplicor v1.5 at follow-up in all strata.</p

Poor concordance between TaqMan v1 and Amplicor v1.5 at low plasma viral load levels (40

<p>–<b>250 HIV RNA copies/mL by TaqMan v1).</b> Between October 2009 and April 2010 plasma samples from British Columbia with low-level viremia (40–250 copies/mL) by the Roche TaqMan v1 assay (N = 1198) were systematically re-tested by the Amplicor v1.5 assay. Poor concordance was observed between TaqMan v1 and Amplicor v1.5 results, with 82% of values falling below the line of identity (red solid line). Points above the blue dashed line are samples in which TaqMan v1 <i>underestimated</i> pVL by ≥0.5 log₁₀ copies/mL relative to the Amplicor v1.5 assay.</p

The proportion of samples detectable by Amplicor v1.5 increases as a function of the TaqMan v1 value.

<p>Of 1198 samples with pVL results 40–250 copies/mL by TaqMan v1, only 34% were detectable when re-tested by Amplicor v1.5 (>50 copies/mL). When TaqMan v1 results were grouped into 50 copies/mL strata we observed a stepwise increase in detectability by Amplicor v1.5 with increasing viral load by TaqMan v1.</p

Patient characteristics of 279 HAART-treated patients with low-level viremia followed longitudinally.

<p>IQR: Interquartile Range.</p