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352 A vignette of discoverythat intervention trials might be feasible, we instituted a standard scheduleof testing blood and urine samples for the presence of CMV virus and measuringanti-CMV antibody titers. CMV infection was defined to be present ifthe CMV virus was isolated in the routine blood and urine tests, or if it wasfound in the course of diagnosing pneumonia, or if antibody titers rose fourfold (seroconverted). Between October 1977 and August 1979, surveillancetesting of blood and urine samples and antibody to CMV was measured in158 patients and their donors prior to transplantation and periodically followingtransplant. The incidence of CMV infection in urine samples was approximatelythe same, regardless of the presence or absence of antibody to CMVbefore transplant, in either the donor or the recipient (Meyers et al., 1980).However, antibody titers increased (as measured by a summary statistic, themean response stimulation index) after 41–60 days following transplant amongpatients who contracted CMV pneumonia (Figure 31.2). Note how the modeof the simulation index among patients with CMV pneumonia coincides withthe time of peak incidence shown in Figure 31.1. Among patients whose CMVtiters were positive pretransplant (seropositive), average titers remained high(see Figure 31.3). But among patients whose pretransplant titers were negative(seronegative), the stimulation index remained low until about 60 daysafter transplant and then began to rise without regard to the marrow donor’spretransplant titer. So although we dismissed the idea that CMV infectionwas being transferred through the donor’s bone marrow, this study suggestedprognostic factors that might be manipulated in an intervention.FIGURE 31.2Mean response of lymphocytes to cytomegalovirus antigen. Numbers in parenthesesrepresent the sample size in each group.