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초록
Background
Xpert Flu (Cepheid, USA) allows for fully automated real-time RT-PCR using a single-use dis-posable cartridge. The aim of this study was to evaluate Xpert Flu for the detection of influenza A virus and subtype A/H1N1/2009 pandemic virus.
Methods
We conducted a prospective comparison study for Xpert Flu with the RealTime ready Influenza A/H1N1 Detection Set (Roche Diagnostics, Germany). Analytical specificities of the assays were determined by testing commonly encountered respiratory viral pathogens, including parainfluenza virus type 1/2/3, rhinovirus A, rhinovirus B, metapneumovirus, adeno-virus, and coronavirus. The analytical sensitivities and workflow of both methods were also assessed.
Results
A total of 102 consecutive clinical specimens were tested by both methods. Total agreement between the two methods was estimated to be 99.0% (101/102): 11 A/H1N1/2009 and 3 seasonal influenza A by the RealTime ready Influenza A/H1N1 Detection Set; 10 and 3 by Xpert Flu. No cross-reactivity was observed between influenza A/H1N1/2009 and other respiratory viral pathogens in either method. The lim-its of detection of the RealTime ready Influenza A/ H1N1 Detection Set and Xpert Flu were 500 TCID50/ mL and 20 TCID50/mL, respectively. Xpert Flu requi-red 85 minutes (10 minutes of hands-on time) for processing, while RealTime ready Influenza A/ H1N1 Detection Set took 128 minutes (30 minutes of hands- on time).
Conclusion
The results of Xpert Flu were compara-ble to those of the RealTime ready Influenza A/H1N1 Detection Set. It is of note that the fully automated and closed system of Xpert Flu could be advanta-geous for reducing hands-on time and for preventing cross-contamination during the testing process.
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Fig. 1.
Workflow analysis of the RealTime ready Influenza A/H1N1 Detection Set and Xpert Flu systems. A, Transfer nasopharyngeal samples into the cartridges; B, RNA extraction and real time RT-PCR in automated Xpert Flu system; C, results analysis; D, sample preparation for RNA extraction; E, RNA extraction using MagNa Pure LC Total Nucleic Acid Isolation Kit; F, Preparation for real time RT-PCR; G, real time RT-PCR using RealTime ready Influenza A/H1N1 Detection Set, H. results analysis.
Table 1.
Xpert Flu (Cepheid, Sunnyvale, CA, USA) performance compared to RealTime ready Influenza A/H1N1 Detection Set (Roche Diagnostics, Mannheim, Germany)
| Xpert Flu | RealTime ready Influenza A/H1N1 Detection Set | |||
|---|---|---|---|---|
| Influenza A | A/H1N1/2009 | Negative | Total | |
| Influenza A | 3 | 0 | 0 | 3 |
| A/H1N1/2009 | 0 | 10 | 0 | 10 |
| Negative | 0 | 1 | 88 | 89 |
| Total | 3 | 11 | 88 | 102 |
Table 2.
Analytical sensitivity of RealTime ready Influenza A/H1N1 Detection Set and Xpert Flu
| Conc. (TCID50∗/mL | RealTime ready Influenza A/H1N1 Detection Set (Ct† value for M2 and N1) | Xpert Flu (Ct value for influenza A/H1N1) | ||||
|---|---|---|---|---|---|---|
| )1 st | 2 nd | 3 rd | 1 st | 2 nd | 3 rd | |
| 500 | Positive (34.1, 32.0) | Positive (34.0, 32.3) | Positive (35.7, 35.1) | Not tested | Not tested | Not tested |
| 250 | Positive (36.1, 34.7) | Positive (35.2, 35.0) | Positive (35.7, 34.4) | Not tested | Not tested | Not tested |
| 200 | Positive (37.0, 35.33) | Positive (37.50, 35.61) | Positive (36.97, 34.95) | Not tested | Not tested | Not tested |
| 150 | Negative (-, 36.77) | Positive (34.01, 36.08) | Negative (-, 36.52) | Not tested | Not tested | Not tested |
| 100 | Negative | Negative | Negative | Positive (32.8, 32.8) | Positive (32.4, 32.4) | Positive (33.1, .33.5) |
| 75 | Not tested | Not tested | Not tested | Positive (35.1, 34.4) | Positive (33.5, 33.5) | Positive (33.4, 34.4) |
| 50 | Not tested | Not tested | Not tested | Positive (39.3, 34.7) | Positive (35.4, 35.5) | Positive (35.7, 35.2) |
| 25 | Not tested | Not tested | Not tested | Positive (35.7, 35.6) | Negative (-, 39.9) | Positive (34.5, 35.6) |
| 10 | Negative | Negative | Negative | Positive (35.7, 35.6) | Negative (-, 37.9) | Negative (-, 37.0) |
| 5 | Not tested | Not tested | Not tested | Negative (-, 35.5) | Negative | Negative |
| 1 | Negative | Negative | Negative | Negative | Negative | Negative |
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