1. A computer-implemented method for determining the probability of the presence of each of a plurality of disease categories for at least one patient, comprising: storing in at least one electronic database: pharmacy claim data for at least one patient; a plurality of drug classes, each including one or more associated drug codes; a plurality of provider specialty categories, each including one or more associated provider specialties; a plurality of disease categories, wherein each disease category is associated with at least one disease or health-related condition; and a plurality of probability equations, one for each stored disease category, wherein each probability equation may be used to calculate a probability that a patient has a specific disease category based upon presence of drug classes and provider specialties in the patient's pharmacy data; for each patient, using a computer processor to assign a first set of variables comprising one variable for each stored drug class, wherein each assigned variable in the first set of variables indicates the presence or absence of at least one drug code associated with the stored drug class in the patient's pharmacy claim data; for each patient, using the computer processor to assign a second set of variables comprising one variable for each stored provider specialty category, wherein each assigned variable in the second set of variables indicates the presence or absence of a provider specialty associated with the stored provider specialty category in the patient's pharmacy claim data; storing the first and second sets of variables for each patient in a data record in the at least one electronic database; using the computer processor to calculate a disease probability value for each patient for each disease category using the respective stored probability equation for the disease category and data from the patient's data record; and storing the calculated disease probability values in each patient's data record in the at least one electronic database.