The relationship between patient knowledge of hemoglobin levels and health-related quality of life.

Background: An anti-anemia drug may improve self-reported quality of life (QOL) partly because patients know their hemoglobin level is rising. In the absence of any published studies on this topic, the authors investigated the association between knowledge of hemoglobin levels and self-reported QOL.Methods: The study analyzed health-related QOL (HRQOL) data from five randomized clinical trials of erythropoietic therapy in patients with cancer-related anemia. Patients were asked whether they knew their hemoglobin level and, if so, to report its value. Patients (n = 1007) were grouped into three categories depending on the extent and accuracy of hemoglobin level knowledge. HRQOL scale scores were compared between categories.Results: Only 23.2% of patients reported knowing their hemoglobin level at the end of the study; however, the value was accurate (within 1 g/dl) in 88.0% of these patients. On five of the 11 HRQOL scales studied, there was a significant association between knowledge of hemoglobin level and HRQOL score. However, the magnitude of the mean difference between those who knew vs. those who did not know their hemoglobin was generally below scale thresholds for minimally important differences. Conclusions: Patient knowledge of hemoglobin level has a modest association with some aspects of self-reported HRQOL. The magnitude of this association, where it exists, would be unlikely to explain large group differences in HRQOL reports over time, even for patients who know their hemoglobin level.