Methods of Information in Medicine 36:1 (1997) 51–58
Among the diagnostic problems that require a retrospective assessment of the time an event occurred is that of screening for primary infection with Toxoplasma gondii during pregnancy. We suggest a method to derive the possible times of onset of infection from a small sequence of serological samples by matching them against the knowledge about possible courses of infection. Special care is taken to properly address the relative change (gradient) of consecutive samples, a nontrivial problem when reasoning about sparsely sampled courses. To demonstrate the practicability of our approach we conducted an evaluation based on the samples of 394 pregnancies selected at random from our toxoplasmosis database; we could show an accuracy of 95.7%.