Contaminated blood cultures may cause results to be misinterpreted, create unnecessary work for the laboratory, and increase costs. Disinfection of the venipuncture site is considered to be necessary for preventing contamination, although there is little information about the effectiveness of using different disinfection materials. The use of 70% isopropyl pads and povidone iodine saturated swabs (conventional method) was compared with the use of a 70% isopropyl/10% acetone scrub and povidone iodine dispenser (PREP method) for skin disinfection. Blood culture "kits" were prepared--bags containing collection tubes, instructions, and either conventional or PREP materials and were distributed randomly. The contents were concealed by a cover to prevent the user from selecting a specific type of decontamination kit. The kits were identified in the laboratory by color-coded labels on the collection tubes. Among 1,546 specimens evaluated, the contamination rate observed with conventional disinfection was significantly higher (4.6%; N = 763) than with PREP materials (2.2%; N = 783, P = 0.011) and was equivalent to the preceding 6-month contamination rate (4.7%). The lower contamination rate may be associated with greater effectiveness of a scrub or isopropyl/acetone solution, or both. Decontamination materials may have a significant impact on reducing blood culture contaminants from skin flora.

The relationship between DNA ploidy and prognostic parameters has been established in prostate cancer. However, comparison of various techniques used for DNA ploidy analysis has not been sufficiently addressed in prostate carcinoma. In the present study, grossly identified discrete carcinoma foci from 48 consecutive radical prostatectomy specimens were analyzed by flow cytometry and image analysis using both imprints and tissue sections. Correlations with other prognostically important pathological findings such as grade, size, extracapsular extension, positive surgical margin, and seminal vesicle and lymph node involvement were done. Image analysis detected 26 (54.2%) nondiploid tumors compared to 15 (31.3%) nondiploid tumors by flow cytometry. No significant differences were demonstrated between imprints and tissue sections. DNA ploidy status showed a good correlation with most other pathological findings listed above. In conclusion, DNA ploidy status determination gives clinically useful information which correlates well with the other useful pathological parameters of prognostic importance. Image analysis may be more sensitive than flow cytometry in detecting nondiploid populations. Tissue sections appear to be as reliable as imprints when properly controlled.

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