A Comparative Study for Detection of EGFR Mutations in Plasma Cell-Free DNA in Korean Clinical Diagnostic Laboratories

Table 3

Unacceptable response rate in pilot external quality assurance scheme.

EGFR variant

Acceptable response/total response

Unacceptable response/total response

Unacceptable response rate (%)

cobas EGFR Mutation Test (7 laboratories)

NGS (2 laboratories)

A

B

C

D

E

F

G

C

F

Level 1

p.L858R; p.E746_ A750del; p.T790M; p.A767_V769dup

4/4

4/4

4/4

4/4

4/4

4/4

4/4

4/4

4/4

0/36

0.0

Level 2

4/4

4/4

4/4

4/4

4/4

4/4

4/4

4/4

4/4

0/36

0.0

Level 3

4/4

4/4

4/4

4/4

4/4

4/4

4/4

2/4

4/4

2/36

5.6

Level 4

-/4

-/4

-/4

-/4

-/4

-/4

-/4

-/4

-/4

Not

-

P-1

p.T790M

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

0.0

P-2

p.L858R

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

0/27

0.0

P-3

p.E746_A750del

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

3/3

0/27

0.0

1~level 4 materials were prepared for a limit of detection and P-1~P-3 materials were prepared for precision evaluation. P-1~P-3 materials were split and run on three replications. cobas assay, p.L858R mutation was detected in one among seven laboratories (14.3%), and p.E746_ A750del (exon 19 deletion) mutation was detected in six among seven laboratories (85.7%). For NGS, exon 19 deletion and p.A767_V769dup (exon 20 insertion) were detected in laboratory F. measurement of P-1 material showed an invalid result in laboratory C. NGS, next-generation sequencing.