Standardization of the methods and reference materials used to assess virus content in varicella vaccines

Table 1 Results of the collaborative study using the national standard (National Institute of Food & Drug Safety Evaluation, code no. 08/027). The virus content test (by plaque staining method) results from the 4 participating laboratories (A, B, C, and D) were compared

Laboratory^a	Robust Z score^b	p-value^*	Multiple Comparison^c
Laboratory^a	Robust Z score^b	p-value^*	A vs. B	A vs. C	A vs. D	B vs. C	B vs. D	C vs. D
A	0.8	<.0001	0.1364	<.0001	<.0001	<.0001	<.0001	0.0063
B	−0.96
C	0.47
D	−0.47

^aLaboratory: one of the participating laboratories, the National Center for Lot Release, Green Cross Corp. (Korea), SK Chemicals (Korea), and Korea Vaccine Co. (Korea) (in randomized order)
^bRobust Z score: unlike the normal Z score, a robust Z score is calculated using the median and absolute deviation from median instead of the mean and standard deviation. When the robust z-score was < |2|, the proficiency of the test laboratories was considered satisfactory
^cMultiple Comparison: p-value adjusted by Bonferroni method
^* P-value: ANOVA test

ISSN: 1743-422X