Characteristics of Deceased Donors
The majority of the analysis in this report is based on a cohort of deceased donors. Because of the focus on organ retrieval, this cohort is restricted to donors who died in Canada and who were referred for retrieval in a Canadian facility. Data from 1991 to 2004 were used (n = 5774).
In order to assess overall patterns of retrieval, a composite measure of organ donation was calculated for each donor. Only the four main organs--heart, lung, liver and kidney--were included in the analysis, as these transplants are the most established and have the highest demand. In terms of retrieval, a donor can score within a range of 0 to 4, where 0 means none of the four organs were retrieved and 4 means all four major organs were retrieved. A further distinction is made for segments, as in the case of liver, and paired organs such as kidney and lungs. In these cases, a liver segment or single kidney (or lung) is given a weight of 0.5. For analysis and presentation, these scores may be grouped into categories of 1 to 4 (0 to 1 = 1, > 1 to 2 = 2, >2 to 3 = 3, and > 3 to 4 = 4). Alternatively, this measure may also be expressed as a mean.
The other primary measure used in the report is the percentage of organs actually transplanted, based on the number of initial organs retrieved. For example, if four organs are retrieved and four are transplanted, the percentage transplanted is 100%; if only two are transplanted, then the percentage would be 50%. But if only two organs are retrieved, and two are transplanted, the percentage transplanted would also be 100%. Although retrieved organs are most often transplanted, this is not always the case, so this measure provides a different perspective on organ utilization.
This first section summarizes some of the basic donor characteristics. Overall, more than half (56%) of donors were male. The majority of donors were Caucasian (81%), with only 4% identified as non-Caucasian (the remainder were of unknown race). The two most dominant blood types were O and A (46% and 40%, respectively), followed by B (11%) and AB (4%).
Table 1 summarizes the age of donors by sex and blood type. The median age of all donors is 41 years, although there is some variation by both race and blood type. Non-Caucasian donors tend to be younger (median = 33), especially if they are type A or AB (medians of 28 and 25, respectively). In contrast, females tend to be older than males, regardless of blood type. Among Caucasian females, those with blood type O have a median age of 45.
The next four figures display variations in age through the use of the boxplot. A boxplot succinctly summarizes a continuous distribution of values by displaying the 25th and 75th percentiles (the lower and upper edges of the box), the extremes of the distribution, the median (represented by the line within the box) and mean, represented by the circle. The sizes of the individual boxes are also proportional to the number of cases.
Figure 2 displays the increasing age of donors between 1991 and 2004. Not only have the mean and median increased, the upper end of donors is higher than 80 years of age in the past few years, a noticeable difference from the early 1990s. Despite the overall increases in age, however, the mean age is typically lower than the median, an indication that donors are still predominantly relatively young.
The age distribution of donors by province of death also reveals some interesting patterns (Figure 3). Donors from Ontario and Quebec tend to be older on average as well as in the extremes, where donors may be 80 or older. In contrast, donors in both the Atlantic provinces and British Columbia are somewhat younger, generally not much older than 70 years of age. British Columbia is also unique among the provinces in that its distribution is virtually symmetrical, since the mean and median are equal and the length of the upper and lower tails are virtually the same.
In Figure 4, the age distributions are categorized by number of organs retrieved from each donor. On average, those who are younger in age are more likely to have more organs retrieved. The upper age range for those with three or four organs retrieved is also less than 75 years, considerably lower than those who have only one or two organs retrieved. As indicated by the width of the boxplots, two or three organs are most often retrieved, followed by one and four.
In addition to retrieval, it is also possible to calculate the proportion of transplants based on organs retrieved. Figure 5 displays age differences among donors in cases where either all or some retrieved organs were transplanted. Overall, there appears to be little difference between the groups; both the means and inter-quartile ranges are almost identical. Although the median age is slightly higher and the upper range is somewhat lower, these differences likely reflect the smaller size of this group. In the vast majority of cases, all retrieved organs are used, so this group will tend to have more atypical cases, thereby increasing the upper end of the age range.