title: Significance of low hematocrit levels in asymptomatic young adults: results of 15 years follow-up.
abstract: OBJECTIVE
  Periodic complete blood counts are not recommended for disease prevention in low-risk, non-pregnant adults. Consequently, there are few follow-up studies of the prevalence of incidentally detected anemia in asymptomatic subjects and its significance for their well-being. The objective of this survey is to determine the frequency of anemia and its predictive value for disease over a 15-yr annual follow-up of a cohort of asymptomatic young males, selected for physical fitness and intelligence.
  
  
  METHODS
  One thousand 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 Hct of 40% or less on two or more tests, and compared the prevalence of diagnosed disorders in subjects with and without anemia.
  
  
  RESULTS
  During follow-up, anemia was found in 125 (12.5%) of the subjects. On successive annual examinations of the same individual Hct levels varied by 3% or more in 3.5% of those without anemia, 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). Anemia was associated with inflammatory bowel disease (OR = 12.1, 95% CI 2.3 78.6) 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 inflammatory bowel 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.
authors.affiliation: Institute of Workers' Health and Department of Epidemiology and Preventive Medicine, Sackler Medical School, Tel Aviv University, Israel.
authors.forename: P
authors.initials: P
authors.lastname: Froom
authors.forename: J
authors.initials: J
authors.lastname: Benbassat
authors.forename: A
authors.initials: A
authors.lastname: Kiwelowicz
authors.forename: J
authors.initials: J
authors.lastname: Erel
authors.forename: B
authors.initials: B
authors.lastname: Davidson
authors.forename: J
authors.initials: J
authors.lastname: Ribak
mesh_terms: D000293:Adolescent; D000328:Adult; D000337:Aerospace Medicine; D000704:Analysis of Variance; D000740:Anemia / Q000097:blood* / Q000150:complications* / Q000453:epidemiology; D002908:Chronic Disease; D005500:Follow-Up Studies; D006400:Hematocrit; D006801:Humans; D015994:Incidence; D007239:Infections / Q000209:etiology; D015212:Inflammatory Bowel Diseases / Q000209:etiology; D007557:Israel / Q000453:epidemiology; D016013:Likelihood Functions; D008297:Male; D008889:Military Personnel; D009369:Neoplasms / Q000209:etiology; D011237:Predictive Value of Tests; D015995:Prevalence; D012307:Risk Factors