Operational definitions improve reliability of the age-related white matter changes scale

BACKGROUND AND PURPOSE

Although the age-related white matter changes (ARWMC) scale has been advocated to be applicable to both MRI and CT for assessing the severity of WMC, its inter-rater reliability on CT is only fair. We aimed to operationalize the ARWMC scale and investigate the effect of this operationalization on the reliability and validity on MRI and CT.

METHODS

Operational definitions of the ARWMC scale were derived from Erkinjuntti research criteria for subcortical vascular dementia and Scheltens scale. Using original and operationalized ARWMC scale, eight observers recorded the time for rating per MRI and per CT. We investigated the inter-rater and intrarater reliability as well as validity against volume using data from 97 stroke patients.

RESULTS

Inter-rater reliability of the operationalized scale on CT (0.874, 95% confidence interval [0.780-0.934]) was better than the original scale (0.569, 95% confidence interval [0.247-0.775]). Its intrarater reliability on CT (0.869) and reliability on MRI (inter-rater: 0.860; intrarater: 0.838) was comparable with the original scale (CT intrarater: 0.750 and on MRI inter-rater: 0.845; intrarater: 0.853). The time required to administer the operationalized scale (4'2″ for MRI and 1'18″ for CT) was similar to that of the original scale (3'56″ for MRI and 1'16″ for CT). The original scale and operationalized scale also significantly correlated with WMC volume (operationalized scale ρ = 0.613, P < 0.001, original scale ρ = 0.638, P < 0.001).

CONCLUSION

Operational definitions improve the inter-rater reliability of ARWMC scale on CT, and it correlates with volumetric measurement.

Generation of recombinant influenza A virus without M2 ion-channel protein by introduction of a point mutation at the 5' end of the viral intron

The aim of this study was to inhibit influenza virus M2 protein expression by mutating the splicing signal of the M gene. Mutations were introduced into the GU dinucleotide sequence at the 5'-proximal splicing site of the M gene (corresponding to nt 52-53 of M cRNA). Transfected cells expressing mutated M viral ribonucleoproteins failed to generate M2 mRNA. Interestingly, recombinant viruses with mutations at the dinucleotide sequence were viable, albeit attenuated, in cell culture. These recombinants failed to express M2 mRNA and M2 protein. These observations demonstrated that the GU invariant dinucleotide sequence at the 5'-proximal splicing site of M gene is essential for M2 mRNA synthesis. These results also indicated that the M2 ion-channel protein is critical, but not essential, for virus replication in cell culture. This approach may provide a new way of producing attenuated influenza A virus.