Benzene exposure and hematopoietic mortality: A long-term epidemiologic risk assessment.

BACKGROUND: Previous studies of a cohort of rubber hydrochloride workers indicated an association between benzene exposure and excess mortality from leukemia and multiple myeloma. To determine whether risks remain elevated with increasing time since plant shutdown, we extended follow-up from 1981 through 1996. MATERIALS AND METHODS: We evaluated risk using standardized mortality ratios (SMR) and generalized Cox proportional hazards regression models. RESULTS: Five new leukemia cases were observed in benzene-exposed white males, but the summary SMR for this group declined from 3.37 (95% CI = 1.54-6.41) to 2.56 (95% CI = 1.43-4.22). In regression models, cumulative exposure was significantly associated with elevated relative risks for leukemia mortality. Four new multiple myeloma deaths occurred, three of which were in workers judged to be unexposed. CONCLUSIONS: These findings reaffirm the leukemogenic effects of benzene exposure and suggest that excess risk diminishes with time.

Effect of follow-up time on risk estimates: a longitudinal examination of the relative risks of leukemia and multiple myeloma in a rubber hydrochloride cohort.

BACKGROUND: Choice of follow-up time for an occupational cohort can influence risk estimates. We examined the effects of follow-up time on relative risk estimates for leukemia and multiple myeloma in a cohort of 1,845 rubber hydrochloride workers. MATERIALS AND METHODS: We generated standardized mortality ratios (SMRs) for yearly follow-ups, beginning each study in 1940 and increasing study end dates from 1950 through 1996. We used Cox proportional hazards modeling to explore the effects of follow-up time on the exposure-response relationship. RESULTS: The SMR for leukemia rose to 13.55 in 1961 and fell nearly monotonically to 2.47 by 1996. Cox modeling suggested interaction between cumulative exposure and time since exposure. A longer time to peak risk was seen for multiple myeloma. CONCLUSIONS: Because summary risk estimates change with follow-up time, exposure limits set using these estimates may not adequately protect workers. Consideration of appropriate follow-up time and use of more complex temporal models are critical to the risk assessment process.

Infection surveillance in home care: device-related incidence rates.

BACKGROUND: Four home health agencies of different sizes, including a rural agency with many branch offices, participated in a surveillance study. METHODS: These agencies used the same definitions for symptomatic urinary tract infections in patients with urinary catheters and for bloodstream infections in patients receiving intravenous therapy. Identical data and methods were used for calculating infection rates, with device-days consistently used as the denominator. Each agency's primary goal was to develop baseline information about its own infection rates and to use these statistics to detect problems and trends. Chart audits were performed if trends or problems were identified. A secondary goal was to compare or benchmark infection rates, because there is almost no published information in this area of home care. RESULTS: We found that our mean infection rates for symptomatic urinary tract infection among patients with urinary catheters and for bloodstream infection among patients receiving intravenous therapy were similar among the four agencies. The mean rates for all four agencies were 4.5 symptomatic urinary tract infections/1000 device-days and 1.1 bloodstream infections/1000 device-days. CONCLUSION: The methods used here can be implemented in other home care agencies. Using the same definitions, collecting data for the same type of infections, and using the same rate calculations make infection control benchmarking possible between home health agencies.

Detection of Chlamydia trachomatis in endocervical specimens by polymerase chain reaction.

A rapid and sensitive polymerase chain reaction (PCR)-based assay for detection of Chlamydia trachomatis in cervical specimens is described. This assay consists of (i) sample preparation which avoids the use of heat, centrifugation, or organic extractions; (ii) rapid, two-temperature PCR amplification of C. trachomatis cryptic plasmid sequences; and (iii) capture and colorimetric detection of amplified DNA in microwell plates. PCR was compared with culture by using 503 cervical specimens. After resolution of discrepant specimens with a confirmatory PCR assay directed against the chlamydial major outer membrane protein gene, PCR had a sensitivity of 97% and a specificity of 99.7% while culture had a sensitivity of 85.7% and a specificity of 100%. In a separate study, PCR was compared with a direct specimen enzyme immunoassay (Chlamydiazyme; Abbott Diagnostics) by using 375 cervical specimens. After resolution of discrepant specimens, PCR had a sensitivity and specificity of 100%, while the enzyme immunoassay had a sensitivity of 58.8% and a specificity of 100%.