PhD thesis - University of Hertfordshire Research Archive

More documents

Recommendations

Info

selected for comparison, it is unlikely that recall bias would differ between these groups, therefore differential recall bias will be minimised or removed. Case-case studies also have disadvantages. By definition, ill cases are not compared with healthy controls and therefore differences in exposure identified through such studies cannot be considered „risk factors‟ for infection in the classical sense. Thus case-case comparisons can generate hypotheses for infection which require confirmation or refutation elsewhere. Similarly, it is not possible to make statements about the direction or magnitude of population risk based solely on the findings of case-case comparisons. In a hypothetical example, both case group A and case group B reported exposure to X, and the level of exposure in group A was significantly higher than for group B, all other factors being equal. The first impression is that exposure X was positively associated with group A. However, it might be equally possible that group B were significantly less likely to report exposure X than the „norm‟, hence the inflated association. Finally, case-case comparisons will not detect risk exposures common to the two groups of cases under comparison. 4.4 Disease determinant analysis. A causal pathway is a theoretical depiction of the relationship between different factors which, alone or in combination, act to alter disease risk for an individual or population. The term „pathway‟ is a misnomer to an extent, as it suggests a straightforward route „from a to b‟, whereas in reality causal pathways tend to exist more as frameworks, with some factors having a direct, or „proximal‟ effect, some having an intermediary effect and some have a more distant, or „distal‟ effect. In an infectious disease context, a rather simplified example of such a pathway would be people of lower socio- economic status (distal) within a particular developing country residing in poorer standard of housing (intermediary), hence having less access to treated water (proximal), which increases their risk of gastrointestinal 31
infection. An approximation of the likely distal and proximal factors applicable to Campylobacter infection in this study are shown in figure 2 below. Figure 2. Distal and proximal factors applicable to Campylobacter infection applicable to this study (illustrative rather than comprehensive). The assessment of the roles of different distal factors, or determinants, for a particular outcome is important in epidemiology, as the potential exists to exert control on that outcome further up the causal pathway. To do so, a population with a particular outcome of interest (the numerator) must be observed and the distribution of the determinants measured, and this distribution compared with that for the underlying population (the denominator) from which the cases arose. As with all epidemiological studies, such comparisons are prone to bias and must therefore be diligently designed and executed. Central to this is the establishment of a population where all individuals with a particular outcome of interest would be easily identifiable, accessible and amenable to measurement, and where the population is sufficiently well-defined in that baseline measurements of suitable deterministic factors has already taken place. 32
Page 1 and 2: Population-Based Sentinel Surveilla
Page 3 and 4: The research carried out by the can
Page 5 and 6: Dedication. This thesis is dedicate
Page 7 and 8: 7. Results (the published work). ..
Page 9 and 10: Statement identifying the degree fo
Page 11 and 12: Paper Reference Page 6 Gillespie IA
Page 13 and 14: Statement of the candidate’s cont
Page 15 and 16: Declaration form. I, Iain Andrew Gi
Page 17 and 18: 2. History. In contrast to other co
Page 19 and 20: The application of veterinary techn
Page 21 and 22: The incidence of laboratory-confirm
Page 23 and 24: were elderly or had a pre-existing
Page 25 and 26: they would for other bacterial gast
Page 27 and 28: papers (Pearson et al., 1977; Bruce
Page 29 and 30: Studies were most frequently conduc
Page 31: The content of peer-reviewed public
Page 35 and 36: hypotheses a „blank canvas‟ app
Page 37 and 38: 6. Materials and methods. Regional
Page 39 and 40: presentation and severity, foreign
Page 41 and 42: together, etc). The results of the
Page 43 and 44: and improve response during the stu
Page 45 and 46: The published work. 7.1 Epidemiolog
Page 47 and 48: community illness was more common a
Page 49 and 50: north west England and in Yorkshire
Page 51 and 52: community was no different from oth
Page 53 and 54: provide useful insights into the ep
Page 55 and 56: Cases in case-control studies of la
Page 57 and 58: 8. Discussion. The research carried
Page 59 and 60: The sentinel health authorities wer
Page 61 and 62: fundamentally flawed. Since the app
Page 63 and 64: control studies. The potential role
Page 65 and 66: Campylobacter spp. from cattle farm
Page 67 and 68: Cameron, S., Ried, K., Worsley, A.,
Page 69 and 70: Doyle, L. P. 1948, "The etiology of
Page 71 and 72: other industrialised countries," in
Page 73 and 74: Hanel, C. M. & Atanassova, V. 2007,
Page 75 and 76: Hudson, S. J., Lightfoot, N. F., Co
Page 77 and 78: Kessel, A. S., Gillespie, I., O'Bri
Page 79 and 80: costs-of-illness, Rijksinstituut vo
Page 81 and 82: Department of Health and Human Serv
Page 83 and 84:
Potter, R. C., Kaneene, J. B., & Ha
Page 85 and 86:
Siemer, B. L., Harrington, C. S., N
Page 87 and 88:
Sopwith, W., Birtles, A., Matthews,
Page 89 and 90:
Campylobacter infection: a general
Page 91:
The published work 90
Page 102 and 103:
101
Page 104 and 105:
103
Page 106 and 107:
105
Page 108 and 109:
107
Page 110 and 111:
109
Page 112 and 113:
111
Page 114 and 115:
113
Page 116 and 117:
115
Page 118 and 119:
117
Page 120 and 121:
119
Page 122 and 123:
121
Page 124 and 125:
123
Page 126 and 127:
125
Page 128 and 129:
127
Page 130 and 131:
129
Page 132 and 133:
131
Page 134 and 135:
133
Page 136 and 137:
135
Page 138 and 139:
137
Page 140 and 141:
139
Page 142 and 143:
141
Page 144 and 145:
Table A1.1: Notable events in the h
Page 146 and 147:
Year Human medicine Veterinary medi
Page 148 and 149:
Levy, A. J. 1928, "A gastro-enterit
Page 150 and 151:
Appendix 2. An assessment of the ro
Page 152 and 153:
compare the period after 2000 with
Page 154 and 155:
condition was significantly associa
Page 156 and 157:
Deaths/100,000 cases 600 500 400 30
Page 158 and 159:
Table A2.1: Factors affecting the u
Page 160 and 161:
Appendix 3. An analytical review of
Page 162 and 163:
to indigenously acquired infection
Page 164 and 165:
susceptibility to Campylobacter inf
Page 166 and 167:
year demonstrated that only the num
Page 168 and 169:
Table A3.1 Reported epidemiological
Page 170 and 171:
Table A3.3 Selected reported risk f
Page 172 and 173:
Table A3.5. The effect of various r
Page 174 and 175:
Deming, M. S., Tauxe, R. V., Blake,
Page 176 and 177:
Harris, N. V., Weiss, N. S., & Nola
Page 178 and 179:
Kist, M. & Rossner, R. 1985a, in Ca
Page 180 and 181:
Oosterom, J., den Uyl, C. H., Banff
Page 182 and 183:
Severin, W. P. J. 1982, "Epidemiolo
Page 184 and 185:
Appendix 4. The Campylobacter Senti
Page 186 and 187:
185
Page 188 and 189:
187
show all

PhD thesis - University of Hertfordshire Research Archive

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?