An apparatus includes a communication interface and a processor. The processor is configured to receive, via the communication interface, a plurality of speech samples {um0}, m=1 . . . M, which were uttered by a subject while in a first state with respect to a disease, and using {um0} and at least one reference discriminator, which is not specific to the subject, synthesize a subject-specific discriminator, which is specific to the subject and is configured to generate, in response to one or more test utterances uttered by the subject, an output indicating a likelihood that the subject is in a second state with respect to the disease. Other embodiments are also described.