Evidence-based evaluation of the risks of malignancy predicted by thyroid fine-needle aspiration biopsies.

A National Cancer Institute (NCI) "Thyroid Fine-Needle Aspiration (FNA) State of the Science Conference" recently proposed standardized nomenclature and "risks of malignancies" associated with various diagnostic categories. We evaluated the evidence levels of the data used by NCI to predict malignancy risks and whether those estimates had clinical validity in our patient population.Eight hundred seventy-nine patients underwent thyroid FNA during 2006. FNA diagnoses were translated into NCI diagnostic categories, and 2-year follow-up retrospective information was obtained. Four percentages of malignancies were calculated for each diagnostic category using follow-up information from FNA, thyroidectomy, both, and all patients as denominators. 95% confidence intervals (CI) were estimated for all proportions, and results were analyzed with chi-square statistics. "Relative risk" calculations were performed using the percentage of malignancies in the entire population under study as a denominator.Most of the studies cited by the NCI provided incomplete and variable level III evidence based mainly on surgical follow-up. Among our patients, the percentages of malignancies calculated with follow-up data from all patients as the denominator were similar to the "risk estimates" proposed by the NCI, but estimates based on surgical follow-up overestimated the probability of thyroid malignancy for patients with FNA diagnosis of "benign" and "follicular lesions of undetermined significance" (FLUS). Relative risk and 95% CI calculations suggested that the NCI classification could be simplified into three categories: "benign," "FLUS + neoplasm," and "suspicious + malignant."

Depression of colony formation by human thymus-derived lymphocytes with rifampin and other antimicrobial agents.

Colonies of human lymphocytes with thymus-derived (T) cell characteristics can be induced in phytohemagglutinin-P to grow in a semisolid medium. To expand the data base on the effects of antimicrobial agents on cell-mediated immunity, the effect of 30 antimicrobial agents on T-lymphocyte cloning was studied. All of the drugs were added to the cultures in concentrations ranging from 10(-5) to 10(-14) M, and the results were compared with those in cultures without the drug. Drugs that inhibit protein synthesis at the 50S ribosomal subunit in bacteria--in particular, chloramphenicol, clindamycin, erythromycin, and troleandomycin--suppressed colony formation. However, the most significantly immunosuppressive agent was rifampin; it suppressed colony formation at concentrations of up to 2.5 x 10(-9) M, a value significantly lower than that found in previous in vitro testing and well below therapeutic levels. Screening of drugs by lymphocyte cloning techniques for possible suppression of cell-mediated immunity appears to be a rapid, sensitive, and inexpensive procedure.