Summary: Infants are common asymptomatic carriers of C. difficile. This incidence of asymptomatic carriage is reported to be as high as 60 percent to 70 percent of infants. These asymptomatic carrier rates probably fall to adult comparable levels between 18 and 24 months of age, but the data are very limited. Consider this before ordering a C. difficile test on a 12-month-old infant in the future.

Q: What is the sensitivity of a Monospot test in children?

The data are very limited on this topic. Approximately 90 percent of adults develop heterophile antibodies, identified by the Monospot test, following an acute Epstein-Barr virus (EBV) infection. Interestingly, though, only about 50 percent of children develop heterophile antibodies following an acute EBV infection.⁷

Only about 50 percent of children develop heterophile antibodies following an acute EBV infection.

A study by Sumaya and Ench looked specifically at the rate of positive heterophile antibody responses in children with confirmed cases of EBV.⁸ The authors evaluated heterophile antibody responses at different ages, stratifying the patients into the following age groups: <2 years, 2–3 years, and ≥4 years. In these age groups, positive heterophile antibody responses were demonstrated in 5.3 percent (1/19), 52 percent (13/25), and 83.6 percent (46/55) of children, respectively. In this single study, the production of heterophile antibodies was near reported adult levels at ≥4 years of age. Overall, children have a relatively poor heterophile antibody response to EBV compared to adults.

A study by Linderholm et al evaluated the sensitivity of a Monospot test in both children and adults.⁹ The authors arbitrarily broke down the groups into ≤12 years and ≥13 years of age. The sensitivity of the Monospot to detect infectious mononucleosis in the 0–12 age group was 38 percent (3/8) compared to 86 percent in the ≥13 years group. It was a very small sample size, and there were only eight patients included in the sensitivity analysis. Overall, there was a poor sensitivity of the Monospot to detect EBV in children 0–12 years of age.

Summary: Ultimately, the Monospot test shows poor sensitivity in children. The limited data that we have suggest that children don’t make near-adult levels of heterophile antibodies until they are at least 4 years of age, resulting in poor Monospot sensitivity. In regard specifically to the Monospot test, the literature suggests that it is not a good test until they are ≥13 years old. For cases where it is important to diagnose mononucleosis and the patient is ≤12 years old, you may want to get the EBV antibody titers additionally or instead.