Table 1.
Identification of basic information for algorithm building using three aetiological factors, potentially translated into criteria for action
| FACTOR 1. Patient term. Useful in STEPS I, II and III (Figure 3). | Probability |
|---|---|
| -Patient has been clinically diagnosed with sCJD, vCJD, gTSE or iCJD |
PxP’ |
| -Patient has not been diagnosed with CJD* but is potentially infective due to: |
PxP’ |
|
a) subclinical CJD* not being excluded; | |
|
b) possibility of existence of prodromal symptoms but no CJD* diagnosis suspected; | |
|
c) his/her being a symptom-free carrier of a pathologic mutation of PRNP, having a family history of CJD or being “at risk of CJD*” for public health purposes; or | |
|
d) CJD* diagnosis suspected owing to clinical symptoms. | |
| where, |
|
|
P= daily incidence of indicated SP among patient’s age- and sex- group; and |
|
|
P’ = prevalence of infective persons among CJD diagnosed, a, b, c or d (A1-7 Figure 3). |
|
|
FACTOR 2. SP putative risk level as a causal risk factor for a specific CJD form, i.e., vCJD, sCJD or iCJD, as defined by contacted tissue. Most useful in STEPS II and III, (Figure 3). |
|
|
-Higher |
P1xP’ |
|
-Lower |
P2xP’ |
|
-Lowest |
P3xP’ |
| Categories defined under a new etiological body-system SP classification |
|
|
Pn = daily incidence of the indicated SP among patient’s age- and sex- group; and, |
|
|
P’ = prevalence of infective persons among patient’s groups (A1-7 Figure 3) undergoing the procedure. |
|
|
FACTOR 3. Patient/SP interaction term (SP with higher than expected incidence late in CJD course).** To be applied for situation appraisal, STEP I (Figure 3). |
|
| **SPs to be identifed from associations reported by quality studies |
|
| For SP categories defined under a body-system SP classification for use as a guide. |
(P2xP’)xA2 |
|
(P3xP’)xA3 | |
| An parameter >1 determined by the magnitude of OR>1** for the indicated SP group or rubric, on termination of incubation period among population converting to CJD* versus population controls. |
* Here CJD constitutes a generic term for different forms of acquired Transmissible Spongiform Encephalopathy (TSE).
** Generated in our study from persons who in fact converted to clinical sCJD in Denmark and Sweden in 1987–2003. In future, this will probably be based on ORs reported in meta-analyses.