1. A method of determining a reliability indicator for at least one set of signatures determined (S1, 101 ) from clinical data collected from a group of samples, the signatures being obtained by detecting characteristics in the clinical data from the group of samples, where each of the signatures generate a first set of stratification values that stratify the group of samples, the method comprising: providing at least one additional and parallel stratification source to the signatures obtained from said group of samples (S2, 103 ), the at least one parallel stratification source being independent from the signatures and generates a second set of stratification values for the group of samples, comparing for each respective sample (S3, 105 ): the first set of stratification values with true reference stratification values, the second stratification values with true reference stratification values, assigning the signatures with similarity measure indicators indicating whether the first and the second stratification values match with the true reference stratification values (S4, 107 ), and implementing the similarity measure indicators as input in determining the reliability of the signatures (S5, 109 ).