Significance of low hematocrit levels in asymptomatic young adults: Results of 15 years follow-up

Hypothesis: Periodic complete blood counts are not recommended for disease prevention in low-risk non-pregnant adults. Consequently, there are few fol low-up studies of the prevalence of incidentally detected anemia in asympto matic subjects and its significance for their well-being. The objective of this survey is to determine the frequency of anemia and its predictive valu e for disease over a 15-yr annual follow-up of a cohort of asymptomatic you ng males, selected for physical fitness and intelligence. Methods: One thou sand Israeli airmen aged 18-30 yr at entry into this historical-prospective study in 1968 were used as subjects. Hematocrit (Hct) levels were examined annually. On the average each subject had 13.2 tests in the course of the 15 yr follow-up. We arbitrarily defined anemia as a Her of 40% or less on t wo or more tests, and compared the prevalence of diagnosed disorders in sub jects with and without anemia. Results: During follow-up, anemia was found in 125 (12.5%) of the subjects. On successive annual examinations of the sa me individual Hct levels varied by 3% or more in 3.5% of those without anem ia, and in 10.5% of those with anemia. The frequency of diagnosed disorders , excluding inter-current infections and trauma, was 25.6% and 10.9% among those with and without anemia, respectively (OR = 2.8, 95% CI 1.8-4.6). Ane mia was associated with inflammatory bowel disease (OR = 12.1, 95% CI 2.3-7 8.6) and malignancy (OR = 3.6, 95% CI 1.1-10.7). It preceded diagnosis only in one case with Waldenstr 246 m's macroglobulinemia, in one case of infla mmatory bower disease and two cases of myocardial infarction. Conclusions: A finding of anemia doubled the likelihood of chronic disease. However, it had a limited predictive value for subsequent morbidity and did not lead to detection of treatable disorders or to disorders that might otherwise have endangered flight safety. Fluctuations of up to 3% in Hct over time may be viewed as normal in young males.