Volume 24, Number 5—May 2018
Dispatch
External Quality Assessment for Zika Virus Molecular Diagnostic Testing, Brazil
Table 1
External quality assessment of 15 laboratories from 7 states of molecular diagnostic testing for Zika virus, Brazil*
| Lab ID | Zika virus, copies/mL3 |
CHIKV | DENV-2 | DENV-4 | JEV | SLEV | WNV | YFV | Plasma | Correct result/no. tested |
|||
| MRS,
8.1 × 105 |
MRS,
7.0 × 103 |
MRS,
1.3 × 103 |
MR766,
2.1 × 103 |
||||||||||
| S-7 |
S-4 |
S-12 |
S-9 |
S-10 |
S-5 |
S-8 |
S-2 |
S-11 |
S-6 |
S-3 |
S-1 |
||
| 3 | + | + | + | + | – | – | – | – | – | – | – | – | 12/12 |
| 11 | + | + | + | + | – | – | – | – | – | – | – | – | 12/12 |
| 12 | + | + | + | + | – | – | – | – | – | – | – | – | 12/12 |
| 13 | + | + | + | + | – | – | – | – | – | – | – | – | 12/12 |
| 1 | + | + | + | (–) | – | – | – | – | – | – | – | 11/12† | |
| 6 | + | + | + | (–) | – | – | – | – | – | – | – | – | 11/12 |
| 10 | + | + | (–) | + | – | – | – | – | – | – | – | – | 11/12 |
| 4 | + | + | (–) | (–) | – | – | – | – | – | – | – | – | 10/12 |
| 7 | + | + | (–) | (–) | – | – | – | – | – | – | – | – | 10/12 |
| 9 | + | + | + | + | – | – | (+) | – | – | (+) | (+) | – | 9/12 |
| 2 | + | + | (–) | (–) | (+) | – | – | (+) | – | – | – | – | 8/12 |
| 14 | + | + | (–) | + | (+) | – | – | – | – | (+) | (+) | (+) | 7/12 |
| 15 | + | (–) | (–) | (–) | – | (+) | – | (+) | (+) | – | – | – | 6/12 |
| 5 | + | + | + | + | (+) | (+) | (+) | (+) | (+) | (+) | (+) | (+) | 4/12 |
| 8 |
+ |
+ |
NT |
+ |
NT |
(+) |
(+) |
(+) |
NT |
(+) |
(+) |
(+) |
3/9 |
| Total‡ | 15/15 (100) | 14/15 (93) | 8/14 (57) | 9/15 (60) | 11/14 (79) | 12/15 (80) | 12/15 (80) | 11/15 (73) | 12/14 (86) | 11/15 (73) | 11/15 (73) | 12/15 (80) | Average 9.2/11.8 |
*Positive samples contained different amounts of Zika virus strain MRS_OPY_Martinique_PaRi_2015 (representing the Asian lineage, including the outbreak strain in the Americas) or Zika virus strain MR766 (representing the African lineage). Zika virus–negative controls contained human plasma, CHIKV, DENV seroypes 2 and 4, JEV, SLEV, WNV, or YFV. Samples were prepared from 0.2 mL phosphate buffered saline supplemented with 20% human plasma and spiked with virus culture supernatants. Viruses were heat inactivated before lyophilization. Human plasma was tested negative for viral RNA and for real-time reverse transcription PCR (RT-PCR) inhibition before spiking of viral cell culture supernatants. Detection of different samples was analyzed by the exact test of goodness-of-fit with p>0.1 being significant. The parameter value defining the expected ratio of correct tests was set to 0.99. Only the 2 samples containing the highest Zika virus loads were tested correctly at statistical significance (p = 1.0 and p = 0.134, respectively). Detection of all other samples showed p values of <0.009. All laboratories except 1 used an assay published by Lanciotti et al. (2). CHIKV, chikungunya virus; DENV, dengue virus; ID, identification number; JEV, Japanese encephalitis virus; NT, samples not tested; S, sample no.; SLEV, St. Louis encephalitis virus; WNV, West Nile virus; YFV, yellow fever virus; +, correct positive result; –, correct negative result; (+), false-positive; (–), false-negative.
†This laboratory used the RealStar Zika Virus RT-PCR Kit (Altona Diagnostics, Hamburg, Germany).
‡Correct results/total results (%).