This paper deals with some basis properties of screening tests. Such tests purport to separate people with disease from people without. Minimal criteria for such a process to be a test are discussed. Various ways of judging the goodness of a test are examined. A common use of tests is to estimate prevalence of disease; frequency of positive tests is shown to be a bad estimate, and the necessary adjustmants are given.

These new follow-up data confirm our previous finding that the TLC regimen of chelation therapy is not associated with neurodevelopmental benefits in children with blood lead levels between 20 and 44 microg/dL (0.96-2.17 micromol/L). These results emphasize the importance of taking environmental measures to prevent exposure to lead. Chelation therapy with succimer cannot be recommended for children with blood lead levels between 20 and 44 microg/dL (0.96-2.12 micromol/L).

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In 1979, a nun poisoning involving 2,000 people occrred in central Taiwan from ingestion of cooking oil contaminated by polyckorinated biphenyls (PCBs) and polyorinatd dibenaofurans (PCDFs). We studied the prevdence of medic conditions in the exposed indivduals and in a neighborhood control group. Statg with a regitry of the exposed individual from 1983, we updated the adesses of exposed individuals and identified a control group matched for age, sex, and neighborhood in 1979. In 1993, individual 30 years of age or older were interviewed by telephone. We obtained usable information from 795 eposed subjects and 693 control subjects.Lifetime prevalence of chloracne, abnormal nails, h s, skin allergy, goiter, headache, gum pigientation and broken teeth were observed more frquenty in the PCBIPCDF-eposed. men and women. The xpos men reported anemia 2.3 times more frequenty than contrls. The exposd men reported arthsitis and heriated intervertebral disks 4.1 and 2.9 times, respectively, more frequendy than controls. There was no dierence i reportd prevalences of other medical conditions. We condude that Taiwanese people exposed to high levels of PCBs and PCDFs reported more frequent medical problems, icuding skin diseas, goiter, anemia, and joint and spine diseases.