Interlaboratory comparison of cytomegalovirus viral load assays.

To assess interlaboratory variability in qualitative and quantitative cytomegalovirus (CMV) viral load (VL) testing, we distributed a panel of samples to 33 laboratories in the USA, Canada and Europe who performed testing using commercial reagents (n = 17) or laboratory-developed assays (n = 18). The panel included two negatives, seven samples constructed from purified CMV nucleocapsids in plasma (2.0-6.0 log(10) copies/mL) and three clinical plasma samples. Interlaboratory variation was observed in both actual (range, 2.0-4.0 log(10) copies/mL) and self-reported lower limits of detection (range, 1.0-4.0 log(10) copies/mL). Variation observed in reported results for individual samples ranged from 2.0 log(10) (minimum) to 4.3 log(10) (maximum)(.) Variation was greatest at low VLs. Assuming +/- 0.5 log(10) relative to the expected result represents an acceptable result, 57.6% of results fell within this range. Use of commercially available reagents and procedures was associated with less variability compared with laboratory-developed assays. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). The significant interlaboratory variability in CMV VL observed may be impacting patient care and limiting interinstitutional comparisons. The creation of an international reference standard for CMV VL assay calibration would be an important step in quality improvement of this laboratory tool.

Interlaboratory comparison of epstein-barr virus viral load assays.

To assess interlaboratory variability in qualitative and quantitative Epstein-Barr virus (EBV) viral load (VL) testing, we distributed a panel of samples to 28 laboratories in the USA, Canada and Europe who performed testing using commercially available reagents (n = 12) or laboratory-developed assays (n = 18). The panel included two negatives, seven constructed samples using Namalwa and Molt-3 cell lines diluted in plasma (1.30-5.30 log(10) copies/mL) and three clinical plasma samples. Significant interlaboratory variation was observed for both actual (range 1.30-4.30 log(10) copies/mL) and self-reported (range, 1.70-3.30 log(10) copies/mL) lower limits of detection. The variation observed in reported results on individual samples ranged from 2.28 log(10) (minimum) to 4.14 log(10) (maximum). Variation was independent of dynamic range and use of commercial versus laboratory-developed assays. Overall, only 47.0% of all results fell within acceptable standards of variation: defined as the expected result +/- 0.50 log(10). Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). Kinetics of change in VL appears more relevant than absolute values and clinicians should understand the uncertainty associated with absolute VL values at their institutions. The creation of an international reference standard for EBV VL assay calibration would be an initial important step in quality improvement of this laboratory tool.

The clinician's approach to evaluating patients with dysrhythmias.

As cardiac arrhythmia services and the ability to perform electrophysiologic testing become more prevalent in the hospital setting, advanced practice nurses (APNs) are continually challenged to keep their skills in evaluating patients with dysrhythmias sharp and current. The experienced APN evaluates the patient's history, recognizes physical findings, and uses noninvasive data to help diagnose, anticipate, and even prevent dysrhythmias. This article reviews the essential components of a systematic evaluation of patients with a known or potential rhythm disturbance.

Serologic responses to hepatitis C virus in solid organ transplant recipients.

BACKGROUND: Hepatitis C (HCV) infection is known to have been transmitted by both blood transfusion and donor organs. We sought to determine the historical incidence of donor- and transfusion-acquired HCV infection in kidney transplant (RTx) and heart transplant (HTx) recipients at our center and to study the kinetics of seroconversion to HCV. METHODS: A bank of sera collected from organ donors (388 RTx and 88 HTx) who received allografts between January 1984 and April 1992 was screened for anti-HCV using a third generation enzyme immunoassay. Recipient sera collected before transplant (preTx), at 1 year after transplant, and at last follow-up were tested. Fresh follow-up sera on all surviving anti-HCV-positive (+) RTx and HTx, all anti-HCV-negative (-) HTx, and a subset of 85 anti-HCV- RTx were assayed for HCV RNA using an reverse transcriptase-polymerase chain reaction assay. RESULTS: Twenty-four of 388 RTx (6.2%) and 2 of 88 HTx (2.3%) were anti-HCV+ preTx. Eight of 218 (3.7%) organ donors were anti-HCV+. Six of the seven (85.7%) anti-HCV+ donors with adequate recipient follow-up transmitted HCV infection to one or more recipients. Nineteen of 313 RTx (6.1%) and 8 of 72 HTx (11.1%) with follow-up > or =1 year seroconverted to anti-HCV. One of 85 (1.2%) anti-HCV- RTx and 3 of 44 (6.8%) anti-HCV-HTx were HCV RNA+ when tested at last follow-up. Five cases of de novo HCV infection occurred after the introduction of first generation anti-HCV screening of donors. Persistent viremia (HCV RNA+) at last follow-up was observed in 70.6% (12/17) RTx anti-HCV+ preTx. Fourteen of 15 (93.3%) RTx and 9 of 9 (100%) HTx with de novo HCV infection had persistent viremia. Seroconversion was more delayed in HTx than RTx (P=0.0572, log-rank Mantel-Cox statistic) although both groups demonstrated an impaired humoral response to HCV when compared with the immunocompetent host. CONCLUSIONS: Organ donor- and transfusion-acquired HCV infection was common in RTx and HTx transplanted before the introduction of second generation anti-HCV screening in 1992. Serologic responses to HCV are often delayed and sometimes absent in these patients. Assays for HCV RNA should be considered as a screening test for the detection of HCV infection in this population. Serologic responses to HCV were more impaired in HTx compared with RTx, which may reflect the more intensive immunosuppressive regimens given to HTx at our center.

A knowledge-based method for protein structure refinement and prediction.

The native conformation of a protein, in a given environment, is determined entirely by the various interatomic interactions dictated by the amino acid sequence (1-3). We describe here a knowledge-based approach for protein structure assessment and prediction. Using a well-defined set of high-resolution protein structures, we have derived statistical potentials, in the form of atom-pairwise distance probability density functions. These provide a description of pairwise interatomic interactions of native proteins. When applied to highly randomized and noisy structures of proteins distinct from the basis set, native-like structures were obtained to very high precision (< or = 2A). The examples tested include proteins of all sizes (from 38 up to 461 amino acids long) and diverse topological structures (alpha, beta and alpha-beta classes). The potentials appear to be sensitive enough to recognize subtle distortions from a native packing structure and in optimization of structures drive them consistently to a higher probability. Therefore they provide a powerful tool for refinement of X-ray and NMR derived structures at arbitrary degrees of initial precision.

Computer aided fluorescence imaging of photosynthetic systems : Application of video imaging to the study of fluorescence induction in green plants and photosynthetic bacteria.

A fluorescence video imaging system utilizing relatively inexpensive commercial components is described. The instrument utilizes a black and white CCD video camera detector, a commercial video imaging board and a IBM-AT compatible computer. The color output of the imaging board greatly aids in the users ability to visually discriminate areas of interest in the video field. Software development that enables the user to capture kinetic traces in real time from the video images is also described. The system is used to monitor fluorescence from photosynthetic systems. The usefulness of the system in screening for photosynthetic mutants is also demonstrated. The cost of the system can be kept below $12,000.

The rate of formation of P700(+)-A 0 (-) in photosystem I particles from spinach as measured by picosecond transient absorption spectroscopy.

Photosystem I particles containing 30-40 chlorophyll a molecules per primary electron donor P700 were subjected to 1.5 ps low density laser flashes at 610 nm resulting in excitation of the antenna chlorophyll a molecules followed by energy transfer to P700 and subsequent oxidation of P700. Absorbance changes were monitored as a function of time with 1.5 ps time resolution. P700 bleaching (decrease in absorbance) occurred within the time resolution of the experiment. This is attributed to the formation of (1)P700.(*) This observation was confirmed by monitoring the rise of a broad absorption band near 810 nm due to chlorophyll a excited singlet state formation. The appearance of the initial bleach at 700 nm was followed by a strong bleaching at 690 nm. The time constant for the appearance of the 690 nm bleach is 13.7±0.8 ps. In the near-infrared region of the spectrum, the 810 nm band (which formed upon the excitation of the photosystem I particles) diminished to about 60% of its original intensity with the same 13.7 ps time constant as the formation of the 690 nm band. The spectral changes are interpreted as due to the formation of the charge separated state P700(+)-A0 (-), where A0 is the primary electron acceptor chlorophyll a molecule.

Effect of bambermycins on quantity, prevalence, duration, and antimicrobial resistance of Salmonella typhimurium in experimentally infected broiler chickens.

Twenty broiler chickens were fed bambermycins (Flavomycin; an antibiotic produced by Streptomyces) at the rate of 3 g/ton (US) for 63 days, and 20 control birds were fed nonmedicated feed. The birds were inoculated (dosed) on the 10th and 11th feeding day with Salmonella typhimurium. The study evaluated the effects of bambermycins on Salmonella incidence, shedding, and antimicrobial resistance. Bambermycins had no effect on body weights, duration of shedding of salmonellae, number of salmonellae shed on postdosing day 3, tissue recoverability of salmonellae, and total number of resistance patterns. Bambermycins resulted in the decrease of salmonellae to be more gradual; however, both treatments were comparable at the end of the study. The majority of S typhimurium from bambermycins-treated birds maintained the original antibiogram of streptomycin, sulfadiazine, and nalidixic acid. The salmonellae isolated from the control birds were more resistant to 2 drugs (varying antibiograms). Bambermycins as a feed additive in broiler diets given at the dose level of 3 g/ton had no detrimental effects based on salmonellae shedding and antimicrobial resistance.

Comparison of therapeutic efficacy of doxycycline, chlortetracycline and lincomycin-spectinomycin on E. coli infection of young chickens.

Three replicate trials were conducted with broiler male chicks to test the therapeutic efficacy of doxycycline, chlortetracycline and lincomycin-spectinomycin in water against an artifically induced Escherichia coli infection. Mortality, lesion scores (heart, liver and air sac), and performance data were the criteria in evaluating therapeutic efficacy of these drugs. Results indicated the therapeutic efficacy of doxycycline was greater than chlortetracycline and lincomycin-spectinomycin.