Ac. Ghani et al., Assessment of the prevalence of vCJD through testing tonsils and appendices for abnormal prion protein, P ROY SOC B, 267(1438), 2000, pp. 23-29
Citations number
21
Categorie Soggetti
Experimental Biology
Journal title
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES
The objective of this study was to determine the age group or groups which
will provide the most information on the potential size of the vCJD epidemi
c in Great Britain via the sampling of tonsil and appendix material to dete
ct the presence of abnormal prion protein (PrPSc). A subsidiary aim was to
determine the degree to which such an anonymous age-stratified testing prog
ramme will reduce current uncertainties in the size of the epidemic in futu
re years. A cohort- and time-stratified model was used to generate epidemic
scenarios consistent with the observed vCJD case incidence. These scenario
s, together with data on the age distribution of tonsillectomies and append
ectomies, were used to evaluate the optimal age group and calendar time for
undertaking testing and to calculate the range of epidemic sizes consisten
t with different outcomes. The analyses suggested that the optimal five-yea
r age group to test is 25-29 years, although a random sample of appendix ti
ssue from all age groups is nearly as informative. A random sample of tonsi
l tissue from all age groups is less informative, but the information conte
nt is improved if sampling is restricted to tissues removed from those over
ten years of age. Based on the assumption that the test is able to detect
infection in the last 75% of the incubation period, zero detected infection
s in an initial random sample of 1000 tissues would suggest that the epidem
ic will be less than 870 000 cases. If infections are detected, then the mo
del prediction suggests that both relatively small epidemics (800+ cases if
one is detected or 8300+ if two are detected) and larger epidemics (21 000
+ cases if three or more are detected) are possible. It was concluded that
testing will be most informative if undertaken using appendix tissues or to
nsil tissues removed from those over ten years of age. Large epidemics can
only he excluded if a small number of infections are detected and the test
is able to detect infection early in the incubation period.