Journal List > Ann Clin Microbiol > v.16(3) > 1078475

Sohn, Park, Kim, Ki, and Lee: Evaluation of the Xpert Flu for the Detection of Influenza A Virus and Influenza A/H1N1/2009 Strain

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.

REFERENCES

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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.
acm-16-140f1.tif
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

Total agreement between the two methods was 99.0% (101/102); positive agreement of Influenza A was 100% (3/3), positive agreement of H1N1/2009 was 90.9% (10/11), negative agreement was 100% (88/88). Kappa value was 0.958 (95% confidence interval 0.877-1).

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

Limit of detection of RealTime ready Influenza A/H1N1 Detection Set and Xpert Flu were 500 TCID50/mL and 20 TCID50/mL, respectively.

50% tissue culture infective dose

Cycle threshold.

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