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Volume 20, Number 1—January 2014
Research

Effects of Drinking-Water Filtration on Cryptosporidium Seroepidemiology, Scotland

Colin N. RamsayComments to Author , Adam P. Wagner, Chris Robertson, Huw V. Smith, and Kevin G.J. Pollock
Author affiliations: Health Protection Scotland, Glasgow, Scotland, UK (C.N. Ramsay, C. Robertson, K.G.J. Pollock); University of Strathclyde, Glasgow (A.P. Wagner, C. Robertson); International Prevention Research Institute, Lyon, France (C. Robertson); Scottish Parasite Diagnostic Laboratory, Glasgow (H.V. Smith)

Main Article

Table 4

The coefficients and significance of the terms used in the second linear mixed effects model fitted to the log of the percentage positive response*

Model element
Coefficient
 Coefficient exponentiated (95% CI)
 % Difference
 (95% CI)
Value (95% CI)
 p alue
Intercept 2.79 (2.61 to 2.98) 0.0000 16.32 (13.57 to 19.63) NA
City† 0.09 (0.02 to 0.15) 0.0077 1.09 (1.02 to 1.17) 19 (5 to 33)
Pre/post filtration periods‡ 0.29 (0.24 to 0.33) 0.0000 1.33 (1.27 to 1.4) 66 (54 to 79)
Period 2 vs. period 1§ 0.16 (0.1 to 0.22) 0.0000 1.17 (1.1 to 1.25) 34 (20 to 49)
Period 4 vs. period 3¶ 0.12 (0.06 to 0.19) 0.0004 1.13 (1.06 to 1.21) 26 (11 to 42)
Pre/postfiltration, Glasgow vs. Dundee# −0.17 (−0.22 to −0.12) 0.0000 0.84 (0.8 to 0.88) −32 (−40 to −23)
Period 2 vs. period 1, Glasgow vs. Dundee** 0.06 (0 to 0.12) 0.0690 1.06 (1 to 1.13) 12 (−1 to −26)
Period 4 vs. period 3, Glasgow vs. Dundee†† 0.07 (0 to 0.14) 0.0475 1.07 (1 to 1.15) 14 (0 to 29)
Minimum donor age‡‡ 0.02 (0.01 to 0.02) 0.0000 1.02 (1.01 to 1.02) NA

*Calculated for study of antibodies against Cryptosporidium spp. in drinking water, Scotland, 2006–2009. NA, not applicable.
†Negative value implies fewer/lower serologic responses in Glasgow than in Dundee, averaged over the 4 periods.
‡Positive value implies more/higher responses in periods 3 and 4 compared with periods 1 and 2, averaged over the periods and cities. Periods 3 and 4 are post filtration in Glasgow.
§Positive value implies more/higher responses during period 2 compared with period 1, averaged over the cities.
¶Positive value implies more/higher responses during period 4 compared with period 3 averaged over the cities.
#Negative value implies fewer/lower responses after filtration (period 3 and 4) at Glasgow than at Dundee. This is a comparison of the change in response from periods 1 and 2 with periods 3 and 4 in Glasgow with the same change in Dundee.
**Positive value implies more/higher change in responses at Glasgow than at Dundee in period 2 compared with period 1.
††Positive value implies more/higher change in responses at Glasgow than at Dundee in period 4 compared with period 3.
‡‡Earliest age at which a sample was collected from a donor.

Main Article

Page created: January 03, 2014
Page updated: January 03, 2014
Page reviewed: January 03, 2014
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