Toward the quantification of α-synuclein aggregates with digital seed amplification assays.

The quantification and characterization of aggregated α-synuclein in clinical samples offer immense potential toward diagnosing, treating, and better understanding neurodegenerative synucleinopathies. Here, we developed digital seed amplification assays to detect single α-synuclein aggregates by partitioning the reaction into microcompartments. Using pre-formed α-synuclein fibrils as reaction seeds, we measured aggregate concentrations as low as 4 pg/mL. To improve our sensitivity, we captured aggregates on antibody-coated magnetic beads before running the amplification reaction. By first characterizing the pre-formed fibrils with transmission electron microscopy and size exclusion chromatography, we determined the specific aggregates targeted by each assay platform. Using brain tissue and cerebrospinal fluid samples collected from patients with Parkinson's Disease and multiple system atrophy, we demonstrated that the assay can detect endogenous pathological α-synuclein aggregates. Furthermore, as another application for these assays, we studied the inhibition of α-synuclein aggregation in the presence of small-molecule inhibitors and used a custom image analysis pipeline to quantify changes in aggregate growth and filament morphology.

Correction to: Second International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions).

The article Second International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions), written by Christoph J Rageth, Elizabeth AM O'Flynn, Katja Pinker, Rahel A Kubik-Huch, Alexander Mundinger, Thomas Decker, Christoph Tausch, Florian Dammann, Pascal A. Baltzer, Eva Maria Fallenberg, Maria P Foschini, Sophie Dellas, Michael Knauer, Caroline Malhaire, Martin Sonnenschein, Andreas Boos, Elisabeth Morris, Zsuzsanna Varga, was originally published electronically on the publisher's internet portal (currently SpringerLink) on November 30, 2018 without open access.

Second International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions).

PURPOSE: The second International Consensus Conference on B3 lesions was held in Zurich, Switzerland, in March 2018, organized by the International Breast Ultrasound School to re-evaluate the consensus recommendations. METHODS: This study (1) evaluated how management recommendations of the first Zurich Consensus Conference of 2016 on B3 lesions had influenced daily practice and (2) reviewed current literature towards recommendations to biopsy. RESULTS: In 2018, the consensus recommendations for management of B3 lesions remained almost unchanged: For flat epithelial atypia (FEA), classical lobular neoplasia (LN), papillary lesions (PL) and radial scars (RS) diagnosed on core-needle biopsy (CNB) or vacuum-assisted biopsy (VAB), excision by VAB in preference to open surgery, and for atypical ductal hyperplasia (ADH) and phyllodes tumors (PT) diagnosed at VAB or CNB, first-line open surgical excision (OE) with follow-up surveillance imaging for 5 years. Analyzing the Database of the Swiss Minimally Invasive Breast Biopsies (MIBB) with more than 30,000 procedures recorded, there was a significant increase in recommending more frequent surveillance of LN [65% in 2018 vs. 51% in 2016 (p = 0.004)], FEA (72% in 2018 vs. 62% in 2016 (p = 0.005)), and PL [(76% in 2018 vs. 70% in 2016 (p = 0.04)] diagnosed on VAB. A trend to more frequent surveillance was also noted also for RS [77% in 2018 vs. 67% in 2016 (p = 0.07)]. CONCLUSIONS: Minimally invasive management of B3 lesions (except ADH and PT) with VAB continues to be appropriate as an alternative to first-line OE in most cases, but with more frequent surveillance, especially for LN.

Initial experience of the BREAST-Q breast-conserving therapy module.

PURPOSE: The most recently developed module of the BREAST-Q, a validated patient outcome measure, is for patients who have undergone breast-conserving therapy (BCT) for cancer. This aim of this study was to assess patient satisfaction and quality of life after BCT using BREAST-Q, investigate clinical risk factors for lower satisfaction and explore the relationship between patient satisfaction with the appearance of their breasts and the other domains of the BREAST-Q. METHODS: Women who had undergone unilateral BCT in the preceding 1-6 years were invited to participate at the time of their annual surveillance mammogram. Clinicopathological data were collected from an electronic database. Linear regression was used to evaluate risk factors for lower satisfaction. Spearman's rho correlation coefficients were calculated to evaluate the relationship between domains. RESULTS: 200 women completed the questionnaire. Mean age was 60 years (SD 11.1). Time from surgery was 35.5 months (SD 17.8). Median score for 'Satisfaction with breasts' was 68 (interquartile range 55-80). Lowest scores were for 'sexual wellbeing' (57, IQR 45-66). On multivariate analysis, BMI at the time of surgery (p = 0.002), delayed wound healing (p = 0.001) and axillary surgery (p = 0.003) were independent risk factors for lower satisfaction. There was significant correlation between 'Satisfaction with breasts' and all other BREAST-Q domains. CONCLUSION: High BMI, delayed wound healing and axillary surgery are risk factors for lower patient satisfaction. This first publication reporting the whole dataset for the BREAST-Q BCT will serve as a benchmark for future studies of patient satisfaction following BCT.

Evaluating the diagnostic sensitivity of computed diffusion-weighted MR imaging in the detection of breast cancer.

PURPOSE: To evaluate the diagnostic sensitivity of computed diffusion-weighted (DW)-MR imaging for the detection of breast cancer. MATERIALS AND METHODS: Local research ethics approval was obtained. A total of 61 women (median 48 years) underwent dynamic contrast enhanced (DCE)- and DW-MR between January 2011 and March 2012, including 27 with breast cancer on core biopsy and 34 normal cases. Standard ADC maps using all four b values (0, 350, 700, 1150) were used to generate computed DW-MR images at b = 1500 s/mm(2) and b = 2000 s/mm(2) . Four image sets were read sequentially by two readers: acquired b = 1150 s/mm(2) , computed b = 1500 s/mm(2) and b = 2000 s/mm(2) , and DCE-MR at an early time point. Cancer detection was rated using a five-point scale; image quality and background suppression were rated using a four-point scale. The diagnostic sensitivity for breast cancer detection was compared using the McNemar test and inter-reader agreement with a Kappa value. RESULTS: Computed DW-MR resulted in higher overall diagnostic sensitivity with b = 2000 s/mm(2) having a mean diagnostic sensitivity of 76% (range 49.8-93.7%) and b = 1500 s/mm(2) having a mean diagnostic sensitivity of 70.3% (range 32-97.7%) compared with 44.4% (range 25.5-64.7%) for acquired b = 1150 s/mm(2) (both p = 0.0001). Computed DW-MR images produced better image quality and background suppression (mean scores for both readers: 2.55 and 2.9 for b 1500 s/mm(2) ; 2.55 and 3.15 for b 2000 s/mm(2) , respectively) than the acquired b value 1150 s/mm(2) images (mean scores for both readers: 2.4 and 2.45, respectively). CONCLUSION: Computed DW-MR imaging has the potential to improve the diagnostic sensitivity of breast cancer detection compared to acquired DW-MR. J. Magn. Reson. Imaging 2016;44:130-137.

Alternative screening for dense breasts: MRI.

OBJECTIVE. The purpose of this article is to review the use of MRI in breast density measurement and breast cancer risk estimation and to discuss the role of MRI as an alternative screening to mammography for screening women with dense breasts. CONCLUSION. The potential of MRI for screening women with dense breasts remains controversial because of the paucity of clinical evidence, the possibility of overdiagnosis, and the cost-effectiveness of the technique in this population. Although methods of MRI measurement require standardization and automation, future addition of MRI density to risk models may positively impact their value.

Diffusion-weighted imaging of the high-risk breast: Apparent diffusion coefficient values and their relationship to breast density.

PURPOSE: To document the apparent diffusion coefficient (ADC) of fibroglandular breast tissue in women at high-risk of developing breast cancer and investigate the relationship between ADC and breast density. MATERIALS AND METHODS: Local research ethics approval was obtained. A total of 33 high-risk women including 17 BRCA1/2 mutation carriers (mean age, 43 years) and 16 women postmantle irradiation (mean age 40 years) underwent diffusion-weighted MRI between days 6 and 16 of their menstrual cycle. ADC histograms from a region of interest in fibroglandular tissue and mammographic breast density measurements were obtained. Mean, percentile ADC values (10th, 25th, 50th, 75th, 90th) and skew were compared for the two groups; ADC and mammographic breast density were correlated. RESULTS: Mean ADC values (×10(-6) mm(2) /s) were 2017 ± 197 in postmantle irradiated women and 1827 ± 289 in BRCA1/2 mutation carriers (P = 0.035) with significant differences at all percentiles (P < 0.0001) but not skew (P = 0.44). ADC values showed weak positive correlation with mammographic breast density in BRCA1/2 mutation carriers (r = 0.51, P = 0.043) but not in postmantle radiotherapy patients (r = 0.49, P = 0.13). CONCLUSION: Higher ADC values seen in fibroglandular tissue postmantle irradiation compared with BRCA1/2 mutation carriers has potential to improve tumor detection in these patients. Lack of correlation between ADC and breast density postmantle irradiation may be a result of microstructural changes.

Cellular mechanisms of heterogeneity in NF2-mutant schwannoma.

Schwannomas are common sporadic tumors and hallmarks of familial neurofibromatosis type 2 (NF2) that develop predominantly on cranial and spinal nerves. Virtually all schwannomas result from inactivation of the NF2 tumor suppressor gene with few, if any, cooperating mutations. Despite their genetic uniformity schwannomas exhibit remarkable clinical and therapeutic heterogeneity, which has impeded successful treatment. How heterogeneity develops in NF2-mutant schwannomas is unknown. We have found that loss of the membrane:cytoskeleton-associated NF2 tumor suppressor, merlin, yields unstable intrinsic polarity and enables Nf2-/- Schwann cells to adopt distinct programs of ErbB ligand production and polarized signaling, suggesting a self-generated model of schwannoma heterogeneity. We validated the heterogeneous distribution of biomarkers of these programs in human schwannoma and exploited the synchronous development of lesions in a mouse model to establish a quantitative pipeline for studying how schwannoma heterogeneity evolves. Our studies highlight the importance of intrinsic mechanisms of heterogeneity across human cancers.

Diffusion weighted imaging of the normal breast: reproducibility of apparent diffusion coefficient measurements and variation with menstrual cycle and menopausal status.

OBJECTIVES: To establish the reproducibility of apparent diffusion coefficient (ADC) measurements in normal fibroglandular breast tissue and to assess variation in ADC values with phase of the menstrual cycle and menopausal status. METHODS: Thirty-one volunteers (13 premenopausal, 18 postmenopausal) underwent magnetic resonance twice (interval 11-22 days) using diffusion-weighted MRI. ADC(total) and a perfusion-insensitive ADC(high) (omitting b = 0) were calculated. Reproducibility and inter-observer variability of mean ADC values were assessed. The difference in mean ADC values between the two phases of the menstrual cycle and the postmenopausal breast were evaluated. RESULTS: ADC(total) and ADC(high) showed good reproducibility (r% = 17.6, 22.4). ADC(high) showed very good inter-observer agreement (kappa = 0.83). The intraclass correlation coefficients (ICC) were 0.93 and 0.91. Mean ADC values were significantly lower in the postmenopausal breast (ADC(total) 1.46 ± 0.3 × 10(-3) mm(2)/s, ADC(high) 1.33 ± 0.3 × 10(-3) mm(2)/s) compared with the premenopausal breast (ADC(total) 1.84 ± 0.26 × 10(-3) mm(2)/s, ADC(high) 1.77 ± 0.26 × 10(-3) mm(2)/s; both P < 0.001). No significant difference was seen in ADC values in relation to menstrual cycle (ADC(total) P = 0.2, ADC(high) P = 0.24) or between postmenopausal women taking or not taking oestrogen supplements (ADC(total) P = 0.6, ADC(high) P = 0.46). CONCLUSIONS: ADC values in fibroglandular breast tissue are reproducible. Lower ADC values within the postmenopausal breast may reduce diffusion-weighted contrast and have implications for accurately detecting tumours. KEY POINTS: • ADC values from fibroglandular breast tissue are measured reproducibly by multiple observers. • Mean ADC values were significantly lower in postmenopausal than premenopausal breast tissue. • Mean ADC values did not vary significantly with menstrual cycle. • Low postmenopausal ADC values may hinder tumour detection on DW-MRI.

Functional magnetic resonance: biomarkers of response in breast cancer.

Functional magnetic resonance (MR) encompasses a spectrum of techniques that depict physiological and molecular processes before morphological changes are visible on conventional imaging. As understanding of the pathophysiological and biomolecular processes involved in breast malignancies evolves, newer functional MR techniques can be employed that define early predictive and surrogate biomarkers for monitoring response to chemotherapy. Neoadjuvant chemotherapy is increasingly used in women with primary breast malignancies to down-stage the tumour and enable successful breast conservation surgery. It also plays a role in the treatment of undetected micrometastases. Cardinal physiological features of tumours that occur as a result of interactions between cancer cells, stromal cells and secreted factors and cytokines and how they change with treatment provide the opportunity to detect changes in the tumour microenvironment prior to any morphological change. Through sequential imaging, tumour response can be assessed and non-responders can be identified early to enable alternative therapies to be considered. This review summarises the functional magnetic resonance biomarkers of response in patients with breast cancer that are currently available and under development. We describe the current state of each biomarker and explore their potential clinical uses and limitations in assessing treatment response. With the aid of selected interesting cases, biomarkers related to dynamic contrast-enhanced MRI, diffusion-weighted MRI, T2*/BOLD and MR spectroscopy are described and illustrated. The potential of newer approaches, such as MR elastography, are also reviewed.

The sonographic twinkling artifact in testicular calcification.

OBJECTIVE: The twinkling artifact is a color Doppler phenomenon that appears as a rapidly fluctuating red and blue Doppler signal behind a strongly reflecting medium, manifesting as a color signal but without real flow behind the structures. To the untrained eye, the twinkling artifact may lead to the misdiagnosis of vascular flow within a structure. Our objective was to show the occurrence of the twinkling artifact in the testis. METHODS: Two patients with calcification in the testis were examined with standard settings on 2 different sonography machines to show this artifact. RESULTS: Calcification in the tunica albuginea and intratesticular macrocalcification both showed this artifact. CONCLUSIONS: We report the presence of the twinkling artifact in 2 cases of testicular calcification, which shows that this phenomenon can occur in the testis.

Dispensing errors and counseling quality in 100 pharmacies.

OBJECTIVE: To evaluate the dispensing accuracy and counseling provided in community chain pharmacies. DESIGN: Cross-sectional study. SETTING: Community chain pharmacies in large metropolitan areas of Florida, Georgia, New Jersey, and New York. PARTICIPANTS: Community chain pharmacies and trained shoppers. INTERVENTIONS: Trained shoppers presented a new prescription order for one of five study drugs to each randomly selected pharmacy, and all encounters with pharmacy staff were recorded on video by ABC News 20/20 staff using hidden cameras. MAIN OUTCOME MEASURES: Dispensing errors on prescriptions for selected medications were the indicator of prescription dispensing accuracy. Frequency of verbal counseling and information categories discussed or included in written information were used to assess the quality of counseling. RESULTS: Of 100 prescriptions dispensed, 22 had one or more deviation from the physician's written order, for a 22% dispensing error rate. Three of the errors were judged to be potentially harmful when dispensed to a typical patient requiring these therapies. A total of 43 shoppers (43%) received verbal counseling, including 16 cases in which the shopper prompted counseling. All shoppers received written information with their prescription, covering an average of 90% of the required topics. Some 68% of the warfarin shoppers purchased aspirin without the pharmacist verbally warning about taking the drugs simultaneously. CONCLUSION: The dispensing error rate of more than one in five prescriptions is similar to the rate found in a similar study conducted 14 years ago, but counseling frequency has decreased significantly during the period.

Threading needles in the dark: the effect of the physical work environment on nursing practice.

Frequently, the most critical calculations, considerations, and preparations for patient care and medication administration are made in noisy, dimly lit, and chaotic areas of the nursing unit. Healthcare has begun to recognize the impact of the physical work environment plays in the ability of humans to perform reliably and safely. This article reviews the draft guidelines recently released by the United States Pharmacopeia for public comment for the physical environment to promote safe medication administration.

Comparison of two error-detection methods in a mail service pharmacy serving health facilities.

OBJECTIVES: To compare two dispensing error-detection methods in a mail service pharmacy and explore clues to the causes of near errors. DESIGN: Descriptive and exploratory study. SETTING: Mail service pharmacy serving health facilities, April 5-9, 2004. PARTICIPANTS: Technicians, pharmacists at a mail service pharmacy; nurses at health facilities served. INTERVENTION: Blinded, undisguised observation of prescription orders at a mail service pharmacy by a research pharmacist and student pharmacist. MAIN OUTCOME MEASURES: Prescription dispensing errors detected by pharmacist audit compared with errors reported by nurses at the health facilities served. RESULTS: Of the 3,337 prescription orders sampled, 16 (0.48%) contained one or more errors based on the observers' assessment and no errors were reported by nurses for these medications using incident reports. Error types detected by observation were compared with the data from incident reports for the 3 previous years. Extrapolating the findings of the observational study and comparing those data with the incident reports, significant differences were found for total dispensing errors, wrong strength errors, wrong dosage form errors, and wrong label instruction errors. Errors related to wrong drug were not significantly different between the observational and incidentreporting data. In observations of pharmacists at work in the mail-service pharmacy, proximity of look-alike/sound-alike drugs on storage shelves and inadequate lighting were potential causes of near errors. CONCLUSION: Pharmacist assessment of prescription orders detects more dispensing errors than nurse-based incident reports. The study identified clues to the causes of near errors occurring in a mail service pharmacy.

Pre-treatment functional MRI of breast cancer: T2* evaluation at 3 T and relationship to dynamic contrast-enhanced and diffusion-weighted imaging.

PURPOSE: Baseline T2* relaxation time has been proposed as an imaging biomarker in cancer, in addition to Dynamic Contrast-Enhanced (DCE) MRI and diffusion-weighted imaging (DWI) parameters. The purpose of the current work is to investigate sources of error in T2* measurements and the relationship between T2* and DCE and DWI functional parameters in breast cancer. METHODS: Five female volunteers and thirty-two women with biopsy proven breast cancer were scanned at 3 T, with Research Ethics Committee approval. T2* values of the normal breast were acquired from high-resolution, low-resolution and fat-suppressed gradient-echo sequences in volunteers, and compared. In breast cancer patients, pre-treatment T2*, DCE MRI and DWI were performed at baseline. Pathologically complete responders at surgery and non-responders were identified and compared. Principal component analysis (PCA) and cluster analysis (CA) were performed. RESULTS: There were no significant differences between T2* values from high-resolution, low-resolution and fat-suppressed datasets (p > 0.05). There were not significant differences between baseline functional parameters in responders and non-responders (p > 0.05). However, there were differences in the relationship between T2* and contrast-agent uptake in responders and non-responders. Voxels of similar characteristics were grouped in 5 clusters, and large intra-tumoural variations of all parameters were demonstrated. CONCLUSION: Breast T2* measurements at 3 T are robust, but spatial resolution should be carefully considered. T2* of breast tumours at baseline is unrelated to DCE and DWI parameters and contribute towards describing functional heterogeneity of breast tumours.

Ultrasound Tomography Evaluation of Breast Density: A Comparison With Noncontrast Magnetic Resonance Imaging.

OBJECTIVES: Ultrasound tomography (UST) is an emerging whole-breast 3-dimensional imaging technique that obtains quantitative tomograms of speed of sound of the entire breast. The imaged parameter is the speed of sound which is used as a surrogate measure of density at each voxel and holds promise as a method to evaluate breast density without ionizing radiation. This study evaluated the technique of UST and compared whole-breast volume averaged speed of sound (VASS) with MR percent water content from noncontrast magnetic resonance imaging (MRI). MATERIALS AND METHODS: Forty-three healthy female volunteers (median age, 40 years; range, 29-59 years) underwent bilateral breast UST and MRI using a 2-point Dixon technique. Reproducibility of VASS was evaluated using Bland-Altman analysis. Volume averaged speed of sound and MR percent water were evaluated and compared using Pearson correlation coefficient. RESULTS: The mean ± standard deviation VASS measurement was 1463 ± 29 m s (range, 1434-1542 m s). There was high similarity between right (1464 ± 30 m s) and left (1462 ± 28 m s) breasts (P = 0.113) (intraclass correlation coefficient, 0.98). Mean MR percent water content was 35.7% ± 14.7% (range, 13.2%-75.3%), with small but significant differences between right and left breasts (36.3% ± 14.9% and 35.1% ± 14.7%, respectively; P = 0.004). There was a very strong correlation between VASS and MR percent water density (r = 0.96, P < 0.0001). CONCLUSIONS: Ultrasound tomography holds promise as a reliable and reproducible 3-dimensional technique to provide a surrogate measure of breast density and correlates strongly with MR percent water content.

Geometric probability distribution for modeling of error risk during prescription dispensing.

PURPOSE: The relationship between the number of prescriptions dispensed by individual pharmacy staff during a single workday and the probability of committing at least one dispensing error during that same workday period was evaluated using a geometric probability distribution. SUMMARY: A cross-sectional descriptive study involving 50 pharmacies located in six cities across the United States was conducted. A pharmacist trained to detect dispensing errors recorded the number of prescriptions filled by each pharmacy staff member and noted which prescription represented the staff member's first dispensing error (defined as any deviation from the prescriber's order) made during the observation period. The Kolmogorov-Smirnov tests for discrete distributions revealed that the observed cumulative distribution of dispensing errors could have come from a geometric probability distribution that assumed dispensing error rates of 2-3%. In terms of risk analysis, this study's findings suggest that there can be a quantifiable statistical relationship between a measure of workload and the risk of committing at least one dispensing error. The ability to model dispensing errors using a geometric probability distribution enables the safety and health care practitioner to directly assess dispensing error risk as a function of a pharmacy's accuracy rate and the number of prescriptions a pharmacy staff member should dispense during a work shift. CONCLUSION: A geometric probability distribution effectively modeled the relationship between the number of prescriptions filled and the occurrence of the first dispensing errors.

Multi-parametric MRI in the early prediction of response to neo-adjuvant chemotherapy in breast cancer: Value of non-modelled parameters.

OBJECTIVE: To prospectively evaluate individual functional MRI metrics for the early prediction of pathological complete response (pCR) to neo-adjuvant chemotherapy (NAC) in breast cancer. MATERIALS AND METHODS: Thirty-two women (median age 52 years; range 32-71 years) with biopsy proven breast cancer due to receive neo-adjuvant anthracycline and/or taxane-based chemotherapy were prospectively recruited following local research ethics committee approval and written informed consent. Breast MRI was performed prior to and after two cycles of NAC and pCR was assessed after surgery. The enhancement fraction (EF), tumour volume, initial area under the gadolinium curve (IAUGC), pharmacokinetic parameters (K(trans), kep and ve), the apparent diffusion coefficient (ADC) and R2* values, along with the percentage change in these parameters after two cycles were evaluated according to pCR status using an independent samples t-test. The area under the receiver operating characteristics curve (AUC) was calculated for each parameter. Linear discriminant analysis (LDA) determined the most important parameter in predicting pCR. RESULTS: A reduction in the EF (-41% ± 38%) and tumour volume (-80% ± 25%) after 2 cycles of NAC were significantly greater in those achieving pCR (p=0.025, p=0.011 respectively). A reduction in the EF of 7% after 2 cycles of NAC identified those more likely to achieve pCR (AUC 0.76). AUC changes in other parameters were tumour volume (0.77), IAUGC (0.64), K(trans) (0.60), kep (0.68), ve (0.58), ADC (0.69) and R2* (0.41). CONCLUSION: In a multi-parametric MRI model, the decrease in a non-model based vascular parameter the enhancement fraction as well as the tumour volume are the most important early predictors of pCR in breast cancer.

Medication errors observed in 36 health care facilities.

BACKGROUND: Medication errors are a national concern. OBJECTIVE: To identify the prevalence of medication errors (doses administered differently than ordered). DESIGN: A prospective cohort study. SETTING: Hospitals accredited by the Joint Commission on Accreditation of Healthcare Organizations, nonaccredited hospitals, and skilled nursing facilities in Georgia and Colorado. PARTICIPANTS: A stratified random sample of 36 institutions. Twenty-six declined, with random replacement. Medication doses given (or omitted) during at least 1 medication pass during a 1- to 4-day period by nurses on high medication-volume nursing units. The target sample was 50 day-shift doses per nursing unit or until all doses for that medication pass were administered. METHODS: Medication errors were witnessed by observation, and verified by a research pharmacist (E.A.F.). Clinical significance was judged by an expert panel of physicians. MAIN OUTCOME MEASURE: Medication errors reaching patients. RESULTS: In the 36 institutions, 19% of the doses (605/3216) were in error. The most frequent errors by category were wrong time (43%), omission (30%), wrong dose (17%), and unauthorized drug (4%). Seven percent of the errors were judged potential adverse drug events. There was no significant difference between error rates in the 3 settings (P =.82) or by size (P =.39). Error rates were higher in Colorado than in Georgia (P =.04) CONCLUSIONS: Medication errors were common (nearly 1 of every 5 doses in the typical hospital and skilled nursing facility). The percentage of errors rated potentially harmful was 7%, or more than 40 per day in a typical 300-patient facility. The problem of defective medication administration systems, although varied, is widespread.