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close this bookBlood Transfusion Services Impact Model and Manual (UNAIDS, 1999, 29 p.)
close this folder1. Introduction to Blood 3.0 and project
View the document1.1 Background
View the document1.2 Key features of Blood 3.0
View the document1.3 Development and distribution of Blood 3.0
View the document1.4 Model Outline

1.4 Model Outline

Figures A, and B (on the following pages) outline the conceptual framework and the main inputs of the model. These are described in more detail in Section 2.2 of the manual.

Figure A outlines the inputs used to describe how the patterns of HIV collection and testing that occur within a particular setting, how this has changed as a result of the intervention, and how this may influence the prevalence of HIV infection among blood transfused. In the figure, text written in italics represents inputs required by Blood 3.0. Text that is not in italics represents information that is calculated from these inputs. For example, the number of units of blood available for transfusion in any year will be dependent upon the total number of units collected; the proportion of blood collected from low risk compared with random donors; the percentage of each that is HIV tested; and the percentage of blood tested that tests HIV negative, and does not test positive for other diseases (such as syphilis or hepatitis).

Figure B outlines the inputs used to estimate the numbers of HIV infections averted among the main groups receiving blood products, and surviving to discharge. Again, text written in italics represents inputs required by Blood 3.0. Text that is not in italics represents information that is calculated from these inputs. Estimates of the prevalence of HIV infection in blood transfused, HIV prevalence among the main recipient groups, and estimates of the distribution of numbers of units provided to the different recipient groups are used to estimate the numbers receiving blood products, and the numbers of HIV infections that may occur. Comparisons between the estimates made in the presence and absence of the intervention are used to estimate the total number of HIV infections averted from the provision of safe blood products. This is combined with inputs describing the percentage of individuals within the main recipient groups surviving to discharge to obtain the final estimates of the total number of HIV infections averted by the intervention.


Sheet A: Blood collection & testing


Sheet A: Blood transfusion