In the study by O’Brien et al., 45 unique and 15 redundant tandem repeat sequences were identified [18]. It was concluded that CA125 consists of at least 60 tandem repeats. However, due to difficulties associated with sequencing repeat regions some may be wrongly positioned or unknown, leaving the exact number of repeats undefined [18]. Furthermore, O’Brien states that the genome database is deficient in repeat information as repetitive sequences were potentially deleted during the compilation process of the human genome [18]. This suggests that the currently available nucleotide sequence of CA125 may not be correct.