Increased Reporting of Detectable Plasma HIV-1 RNA Levels at the Critical Threshold of 50 Copies per Milliliter With the Taqman Assay in Comparison to the Amplicor Assay
Bibliographic record
Abstract
OBJECTIVE: To investigate the application of the new COBAS Ampliprep Taqman HIV-1 assay in comparison with the COBAS HIV-1 Ampliprep AMPLICOR MONITOR ultrasensitive assay version 1.5, with a particular focus on the most clinically relevant region near the lower limit of quantification. METHODS: Scatterplots and the Bland-Altman plot were used to inspect the degree of agreement between the 2 assays when tested on samples from the British Columbia Centre for Excellence in HIV/AIDS monitoring and evaluation system. Consistency of clinically applicable values at low HIV-1 RNA copy number was assessed from samples from individuals with previously undetectable Amplicor results. RESULTS: Despite general agreement of these assays over a wide dynamic range, the Taqman assay resulted in a nearly 2-fold increase (from 3.6% to 6.9%) in the number of patients experiencing a plasma HIV-1 RNA level >50 copies per milliliter after being suppressed to levels <50 copies per milliliter consistently during the previous year (P < 0.01). In addition, rare discrepancies between the 2 assays were observed to be as high as 0.7 log10 copies per milliliter. The kappa statistic was 0.19, indicating only slight agreement at the critical threshold of 50 HIV RNA copies per milliliter, with 43% of undetectable samples in the Amplicor assay testing detectable in the Taqman assay (median 70 copies/mL; interquartile range 60-83 copies/mL). CONCLUSIONS: The increased frequency of detectable plasma HIV-1 RNA levels at the threshold of 50 copies per milliliter with the new Taqman assay has important implications for highly active antiretroviral therapy monitoring. Until there is clinical evidence that patients with detectable HIV by the Taqman assay (but undetectable HIV with Amplicor) have differential outcomes, it is unclear whether the Taqman assay is appropriate for routine management of HIV-1 therapy, and caution is required in the interpretation of low-level viremia by the Taqman assay until a clinical validation of a new cutoff is performed.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".