Long-term stability of CMV DNA in human breast milk.

BACKGROUND: Human cytomegalovirus (CMV) is the leading cause of intrauterine and perinatal viral infection. The most common route of CMV transmission in newborns is through breastmilk and this can lead to infant morbidity and mortality. Breast milk that has been frozen for an extended period may need to be tested for CMV DNA to determine the source of infection. It has been a challenge for clinical laboratories to ensure the stability of CMV DNA in frozen breast milk for accurate viral load measurement. OBJECTIVES: To evaluate the stability of CMV DNA in breast milk by testing quantitative viral loads over a 28-day period for breast milk stored at 4 °C and a 90-day period for breast milk stored at -20 °C. STUDY DESIGN: Baseline viral loads were determined on day 0 and the samples stored at 4 °C underwent extraction and amplification at four time points, up to 28 days. The samples stored at -20 °C underwent extraction and amplification at five time points up to 90 days. Log10 values were calculated and t-test, Pearson's coefficient, and concordance correlation coefficient were calculated. RESULTS: There was no statistically significant difference between the time points by t-test, and correlation coefficients showed greater than 90% concordance for days 0 and 28 as well as days 0 and 90 at both storage temperatures tested. CONCLUSIONS: The concentration of CMV DNA in breast milk was stable for 28 days at 4 °C and 90 days at -20 °C as the concentrations did not differ significantly from the baseline viral loads.