Age- and sex-specific patterns of microcytic anemia in adolescence: implications for screening

To characterize age- and sex-specific patterns of microcytic anemia during adolescence and to estimate the potential yield of screening across age groups. We performed a retrospective Electronic Health Record (EHR)-based study using data from Clalit Health Services (CHS), the largest health maintenance organization in Israel. Adolescents aged 12-18 years with at least one hemoglobin and mean corpuscular volume (MCV) measurement between 2003 and 2023 were included. Individuals with hereditary, hemolytic, or chronic inflammatory causes of anemia were excluded. Microcytic anemia was defined as hemoglobin < 12 g/dL for females and < 13 g/dL for males with MCV < 78 fL. Age- and sex-specific prevalence was calculated among tested adolescents and in the total CHS-insured population. Screening efficiency was assessed using the number needed to test (NNT). A total of 1,306,623 test records were analyzed. Among females, the prevalence of microcytic anemia increased with age, from 7.8% at ages 12-13 to 12.5% at ages 17-18. Among males, prevalence declined from 18.9% at age 12-13 to 2.1% at ages 17-18. This resulted in a reversal of the sex distribution of microcytic anemia prevalence during mid-adolescence, with females exceeding males from approximately age 15 onward. The NNT increased with age among males and remained relatively stable during mid- to late adolescence among females.

Microcytic anemia demonstrates distinct age- and sex-specific patterns during adolescence. The increasing prevalence among females and declining prevalence among males suggest that targeted screening of adolescent girls during mid-adolescence may be an efficient strategy for identifying microcytic anemia, a condition commonly associated with iron deficiency in this age group.

• Iron deficiency anemia remains common in adolescents, particularly among females in high-income countries. • Prevalence estimates vary widely due to differences in definitions, populations, and study designs. • There are no universally accepted guidelines for routine anemia screening in adolescents, and current practices are inconsistent.

• A reversal in sex-specific prevalence of microcytic anemia occurs during mid-adolescence, with higher rates in females from approximately age 15 onward. • Screening efficiency, quantified by number needed to test, varies substantially by age and sex, supporting targeted screening of adolescent girls at age 14.