| Autor: |
De Bel, Annelies, Marissens, D., Debaisieux, L., Liesnard, C., Van Den Wijngaert, Sigismond, Piérard, Denis, Lauwers, Sabine |
| Přispěvatelé: |
Immunology and Microbiology |
| Jazyk: |
angličtina |
| Rok vydání: |
2009 |
| Předmět: |
|
| Popis: |
Background: The HIV-1 viral load (VL) assay is a major tool in the follow-up of HIV-infected individuals. Classical end-point amplification techniques for VL are more and more replaced by real-time technologies. Initial evaluations of the Cobas Ampliprep/Cobas Taqman (CAP/CTM) v1.0 assay were good but afterwards reports about serious underquantification became available. The aim of this study was to investigate if the underquantification problem is solved with the second version of this CAP/CTM assay. Materials & Methods: 381 consecutive HIV-1 positive samples with VL ?4000 copies/ml with Cobas Amplicor were collected in 3 labs. Only one sample per patient was included. The left over material after routine testing of the original specimen was diluted 1:5 or 1:10, aliquoted and tested in parallel with Cobas Ampliprep/Cobas Amplicor (CAP/CA) v1.5, CAP/CTM v1.0 and v2.0. An absolute difference between the results of two methods of more than 0.7 log copies/ml was defined as moderately discrepant and an absolute difference of more than 0.9 log copies/ml was defined as severely discrepant. Criteria to be fulfilled for considering the new methods equivalent to the routine method were as follows: an absolute difference between CAP/CA and respectively CAP/CTM v1.0 and v2.0 of less than 0.7 log c/ml for at least 95% and less than 0.9 log c/ml for at least 99% of all samples. Mean values (log copies/ml) were compared with the t-test for paired data. Results: One sample appeared severely overquantitated with both Taqman assays (+1.29 and +1.84 log copies/ml with v1.0 and v2.0 respectively). This is probably due to a primer mismatch and underquantification with the CAP/CA assay. The patient's CD4 count and clinical presentation correlate better with the higher VL. This result was considered as an outlier and was not taken into account in our calculations. CAP/CTM v1.0 compared to CAP/CA: 36 (9.5%) samples were moderately and 20 (5.3%) samples were severely underquantitated. 2 (0.5%) samples were moderately overquantitated. The overall mean difference between CAP/CTM v1.0 and CAP/CA was -0.32 log copies/ml. This difference is statistically significant. Although this difference is less than 0.5 log copies/ml, accepted as clinically relevant, it clearly illustrates the underquantification problem. Moreover, the number of moderately and severely underquantitated samples is unacceptable. CAP/CTM v2.0 compared to CAP/CA: No samples were moderately or severely underquantitated. 8 (2.1%) samples were moderately and 3 (0.8%) were severely overquantitated. A mean difference of +0.07 log copies/ml was found with the CAP/CTM v2.0 compared to CAP/CA. This difference is statistically but not clinically significant. Conclusions: The criteria to consider the new method equivalent to the routine method are fulfilled only for CAP/CTM v2.0. In this evaluation the underquantification problem with the first version of the CAP/CTM kit was clearly demonstrated and it seems to be solved with the second version of this kit. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
