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PubMed1992

Within and between observer agreement on ultrasonic evaluation of bovine ovarian structures.

A diagnostic ultrasound unit with a 5 MHz probe was used to examine ovarian structures in vitro from 32 reproductive tracts obtained at slaughter from young cows. Agreement between and within observers, and between observers and dissection results was evaluated using the kappa statistic. Agreement was high (kappa from 0.531 to 0.969) for all evaluations of corpora lutea. The sensitivity, specificity and predictive value of both positive and negative findings for presence of a corpus luteum was > 0.9. Agreement between and within observers was little better than chance for follicles measuring 4 to < 6 mm and for follicles measuring 6 to < 10 mm. However, agreement between observers and dissection results indicated that observers could detect follicles 4 to < 6 mm and 6 to < 10 mm (kappa 0.301 to 0.731 and 0.414 to 0.612, respectively). Kappa values within and between observers and between observers and dissection results for observations of follicles measuring > or = 10 mm were almost all > 0.4 indicating that large follicles can be readily detected using ultrasound. It is suggested that further validation of ultrasound methods is needed to determine whether follicles measuring < 4 mm can be accurately identified, and whether follicles can be accurately identified and monitored over a number of days. The ultrasound unit was useful for detecting the presence of corpora lutea and follicles. However, agreement between and within observers on the presence of follicles measuring < 10 mm was poor.

Animals↗

PubMed2006

Experimental determination of subjective similarity for pairs of clustered microcalcifications on mammograms: observer study results.

Presentation of images of lesions similar to that of an unknown lesion might be useful to radiologists in distinguishing between benign and malignant clustered microcalcifications on mammograms. Investigators have been developing computerized schemes to select similar images from large databases. However, whether selected images are really similar in appearance is not examined for most of the schemes. In order to retrieve images that are useful to radiologists, the selected images must be similar from radiologists' diagnostic points of view. Therefore, in this study, the data of radiologists' subjective similarity for pairs of clustered microcalcification images were obtained from a number of observers, and the intra- and inter-observer variations and the intergroup correlations were determined to investigate whether reliable similarity ratings by human observers can be determined. Nineteen images of clustered microcalcifications, each of which was paired with six other images, were selected for the observer study. Thus, subjective similarity ratings for 114 pairs of clustered microcalcifications were determined by each observer. Thirteen breast, ten general, and ten nonradiologists participated in the observer study; some of them completed the study multiple times. Although the intraobserver variations for the individual readings and the interobserver variations for pairs of observers were not small, the interobserver agreements were improved by taking the average of readings by the same observers. When the similarity ratings by a number of observers were averaged among the groups of breast, general, and nonradiologists, the mean differences of the ratings between the groups decreased, and good concordance correlations (0.846, 0.817, and 0.785) between the groups were obtained. The result indicates that reliable similarity ratings can be determined by use of this method, and the average similarity ratings by breast radiologists can be considered meaningful and useful for the development and evaluation of a computerized scheme for selection of similar images.

Breast Diseases↗

PubMed2006

Investigations of the reliability of observational gait analysis for the assessment of lameness in horses.

The objectives of this study were to assess the reliability of a numerical rating scale (NRS) and a verbal rating scale (VRS) for the assessment of lameness in horses and to determine whether they can be used interchangeably. Sixteen independent observers graded the severity of lameness in 20 videotaped horses, and the agreement between and within observers, correlation and bias were determined for each scale. The observers agreed with each other in 56 per cent of the observations with the NRS and in 60 per cent of the observations with the VRS, and the associated Kendall coefficient of concordance was high. Similar trends were evident in the agreement between two observations by each observer. The correlation between and within observers was high for both scales. There were no significant differences (bias) among the observers' mean scores when using either scale. There was a significant correlation between the lameness scores attributed when using the two scales, but the differences between the scores when plotted against their overall mean were unacceptable for clinical purposes. The results indicate that the NRS and VRS are only moderately reliable when used to assess lameness severity in the horse, and that they should not be used interchangeably.

Animals↗

PubMed1999

Ovarian cancer: comparison of observer performance for four methods of interpreting CT scans.

PURPOSE: To assess the effects of four interpretative methods on observers' mean sensitivity and specificity by using computed tomography (CT) of ovarian carcinoma as a model. MATERIALS AND METHODS: CT scans in 98 patients with ovarian carcinoma and 49 women who were disease free were retrospectively reviewed by four experienced blinded radiologists to compare single-observer reading, single-observer reading with an anatomic checklist, paired-observer reading (simultaneous double reading), and replicated reading (combination of two independent readings). Confidence level scoring was used to identify three possible disease forms in each patient: extranodal tumor, lymphadenopathy, and ascites. Patient conditions were then categorized as abnormal or normal. RESULTS: There were no significant improvements in sensitivity or specificity for classification of patient conditions as abnormal or normal when comparing single-observer interpretation with single-observer interpretation with a checklist or paired-observer interpretation. Although there was no significant improvement in the mean sensitivity (93% vs 94%) by using the replicated reading method, there was a statistically significant improvement in mean specificity (85% vs 79%) for the replicated readings compared with single-observer interpretations (P < .05). CONCLUSION: Diagnostic aids such as checklists and paired simultaneous readings did not lead to an improved mean observer performance for experienced readers. However, an increase in the mean specificity occurred with replicated readings.

Female↗

PubMed1999

Carotid plaque characterization by duplex scanning: observer error may undermine current clinical trials.

BACKGROUND AND PURPOSE: Clinical studies currently in progress are using subjective methods to characterize plaque morphology from ultrasound images. However, there are few studies on the intraobserver and interobserver variability of these classifications. This study was designed to assess these variables. METHODS: Grading of plaque morphology from ultrasound images, stored both digitally and to hard copy, was performed by 2 classification schemes. Interobserver agreement was determined by 4 observers. Within-observer agreement was performed at intervals for up to 6 months. Accuracy of the 2 methods was determined by comparison with histology. RESULTS: Within- and between-observer agreement was moderate to good for full-color digital image analyses, with pooled kappa values of kappap=0.49+/-0.10 and kappap=0.62+/-0.07 for the 2-category method and kappap=0.53+/-0.06 and kappap=0.52+/-0.05 for the 4-category method, respectively. Hard copy data analyses gave lower kappa values. The more experienced observers produced higher within-observer agreements and higher correlation with histology. CONCLUSIONS: Reproducible grading of ultrasound images is not consistently achievable among experienced observers, and within-observer agreement may vary with time. The current subjective ultrasound characterization of carotid plaque morphology used in clinical trials may be associated with unacceptable levels of reproducibility in some centers. Variability between observers may be reduced by using the simpler 2-category grading of plaque morphology to interrogate full-color digitally stored images. Observer agreement should be audited regularly.

Aged↗

PubMed2000

Utilization and outcome in an overnight psychiatric observation program at a Veterans Affairs Medical Center.

OBJECTIVE: The effectiveness of an overnight psychiatric observation program was evaluated. The program was designed to avoid unnecessary hospitalization of patients experiencing acute psychiatric crises. METHODS: Of 110 patients admitted to the observation unit at a Veterans Affairs medical center over a six-month period in 1996, the charts of 92 patients were retrospectively reviewed. Characteristics of patients referred to the program were documented, inpatient hospitalization rates and suicide rates in the six-month periods before and after admission to the observation unit were examined, and variables related to the need for hospitalization immediately after observation were explored. RESULTS: Most of the 92 patients (98 percent) were referred from the medical center's emergency room. At the time of observation, 80 percent of the patients were unemployed, 55 percent expressed suicidal or homicidal ideation, 49 percent were intoxicated or at risk for alcohol withdrawal, and 41 percent were homeless. The most frequent psychiatric diagnosis was substance abuse or dependence (77 percent). The large majority of patients (88 percent) were referred the next day to other outpatient programs for follow-up and treatment, which avoided costly inpatient treatment. In the six months before admission to the observation program, the mean number of inpatient psychiatric bed days was 9.8, compared with 2.7 days in the six-month period after discharge from the observation program. No increase in suicide gestures or attempts was noted among the patients. No variables significantly predicted admission to inpatient care after the observation period. CONCLUSIONS: Overnight observation programs may provide a cost-effective alternative to traditional inpatient treatment for some individuals with psychiatric disorders.

Adult↗

PubMed2006

Observation of perceived exertion in children using the OMNI pictorial scale.

PURPOSE: Concurrent and construct validity of a kinematic exertional observation procedure was examined for 10- to 14-yr-old female (N = 22) and male (N = 22) healthy children. METHODS: A load-incremented treadmill test protocol employing speed/grade changes every 3 min was used. RPE for the overall body (RPE-Overall), legs (RPE-Legs), and chest (RPE-Chest) were simultaneously estimated by an independent observer and self-rated by a subject during each treadmill stage using the Children's OMNI-Walk/Run Scale. Subjects' HR and oxygen consumption (VO2) were measured during each stage. Concurrent validity was established by correlating the observer's RPE with the subject's HR and VO2. Construct validity was examined by correlating submaximal RPE estimated by the observer with RPE estimated by the subject. RESULTS: The range of responses for the females and males was VO2 = 18.4-43.5 mL x kg(-1) x min(-1), HR = 121-185 bpm, and OMNI Scale RPE- (Overall, -Legs, -Chest) ranging from 1 to 9. Observer RPE (Overall, -Legs, -Chest) for the female and male subjects ranged from 1 to 9. For both female and male groups regression analyses indicated that observer's RPE distributed as a positive function of subject's HR and VO2; r = 0.80-0.91 (P < 0.01). Observer's RPE distributed as a positive function of subject's RPE for both females and males; r = 0.87-0.92 (P < 0.01). CONCLUSION: Results support the validity of a direct kinematic observation procedure to estimate OMNI Scale RPE for female and male children performing treadmill exercise. Exertional observation provides an unobtrusive perceptual estimate of exercise intensity and could be included in standardized physical activity assessments for children.

Adolescent↗

PubMed1996

Methods of reducing observer variation in age estimation from panoramic radiographs.

OBJECTIVE: To compare inter- and intra-observer variation in age estimation using subjective and objective methods. METHODS: Fifty-six panoramic radiographs of patients aged 13 to 25 years were assessed subjectively twice by four observers for the stage of root development of the lower third molars on a seven-point scale. Two of the observers were calibrated before the first evaluation, and the other two before the second. The same observers also digitized predefined reference points in a subsample of the third molars ten times by means of a computer-based digitizer system. Observer variation in classifying different root stages and in digitizing coordinates and measuring root lengths were studied. RESULTS: Significant systematic differences existed between two of the observers in the subjective assessment. One non-pre-calibrated observer changed her pattern most. Scattergrams from the digitizer measurements showed a good precision within and between observers with no significant differences in calculating root lengths. When, however, the teeth were analysed separately, some significant differences were found. CONCLUSIONS: The overall observer agreement was best using the objective method on several teeth. With only one tooth there were some significant differences. Subjective evaluation was improved by prior calibration.

Adolescent↗

PubMed1992

Effect of random background inhomogeneity on observer detection performance.

Many psychophysical studies of the ability of the human observer to detect a signal superimposed upon a uniform background, where both the signal and the background are known exactly, have been reported in the literature. In such cases, the ideal or the Bayesian observer is often used as a mathematical model of human performance since it can be readily calculated and is a good predictor of human performance for the task at hand. If, however, the background is spatially inhomogeneous (lumpy), the ideal observer becomes nonlinear, and its performance becomes difficult to evaluate. Since inhomogeneous backgrounds are commonly encountered in many practical applications, we have investigated the effects of background inhomogeneities on human performance. The task was detection of a two-dimensional Gaussian signal superimposed upon an inhomogeneous background and imaged through a pinhole imaging system. Poisson noise corresponding to a certain exposure time and aperture size was added to the detected image. A six-point rating scale technique was used to measure human performance as a function of the strength of the nonuniformities (lumpiness) in the background, the amount of blur of the imaging system, and the amount of Poisson noise in the image. The results of this study were compared with earlier theoretical predictions by Myers et al. [J. Opt. Soc. Am. A 7, 1279 (1990)] for two observer models: the optimum linear discriminant, also known as the Hotelling observer, and a nonprewhitening matched filter. Although the efficiency of the human observer relative to the Hotelling observer was only approximately 10%, the variation in human performance with respect to varying aperture size and exposure time was well predicted by the Hotelling model. The nonprewhitening model, on the other hand, fails to predict human performance in lumpy backgrounds in this study. In particular, this model predicts that performance will saturate with increasing exposure time and drop precipitously with increasing lumpiness; neither effect is observed with human observers.

Diagnostic Imaging↗

PubMed2005

The pediatric hybrid observation unit: an analysis of 6477 consecutive patient encounters.

OBJECTIVES: Pediatric observation units (OUs) are becoming more common in hospitals throughout the United States, providing physicians with a new disposition option for children who are judged to be too ill for home management. Some OUs function as "hybrid" units, serving both acutely ill and injured observation patients as well as scheduled elective procedure patients. How best to utilize this new resource is not yet defined. We studied the utilization of our pediatric hybrid OU during the first 2 years of operation to determine (1) the spectrum and frequency of diagnoses treated, (2) diagnoses and procedures most (and least) likely to attain discharge successfully within 24 hours, and (3) whether age was associated with inability to be discharged from the OU within 24 hours. METHODS: The study setting was a 20-bed hybrid OU located in a pediatric tertiary care hospital in Salt Lake City, Utah. The records of all patients admitted during the first 2 years of OU operation, from August 1999 through July 2001, were examined retrospectively. RESULTS: There were 6477 OU admissions: 4189 (65%) for acutely ill and injured observation patients and 2288 (35%) for scheduled elective procedure patients. For the observation patients, median age was 2.5 years and median length of stay was 15.5 hours. Common admission diagnoses in these patients included enteritis/dehydration (n = 722), orthopedic injuries (n = 362), asthma (n = 327), closed head injury (n = 289), urgent transfusion/infusion (n = 221), bronchiolitis (n = 212), croup (n = 207), abdominal pain (n = 199), cellulitis (n = 177), and nonfebrile seizure (n = 98). Overall, 15% of observation patients required subsequent inpatient admission for >24-hour stay. Observation diagnoses that were most likely to require inpatient admission were hematochezia (60%), viral pneumonia (46%), and bronchiolitis (43%). We demonstrated successful OU discharge rates (>85%) for several diagnoses not commonly reported: neonatal hyperbilirubinemia, aseptic meningitis, and diabetic ketoacidosis in the patient with known diabetes. Among the scheduled elective procedure patients, median age was 5.0 years and median length of stay was 3.0 hours. Only 1% of these patients required subsequent inpatient admission. In both populations, age < or =30 days was associated with increased need for inpatient admission, with a relative risk of 1.9 (95% confidence interval: 1.4-2.6) among the observation patients and 13.9 (95% confidence interval: 3.0-65.0) among scheduled procedure patients. CONCLUSION: Our pediatric hybrid OU played an important role in the treatment of children who were admitted for observation as a result of acute illness or injury, as well as children who required scheduled procedures. For both patient types, we identified diagnoses that are most and least likely to attain successful discharge within 24 hours. The majority (85%) of observation patients were discharged successfully within 24 hours. Successful discharge rates for diagnoses that are not commonly managed in other pediatric OUs were reported. We identified certain age groups within selected diagnoses that may not have been appropriate for the OU.

Adolescent↗

PubMed2002

Observing behavior: effects of rate and magnitude of primary reinforcement.

Four experiments examined the free-operant observing behavior of rats. In Experiment 1, observing was a bitonic function of random-ratio schedule requirements for the primary reinforcer. In Experiment 2, decreases in the magnitude of the primary reinforcer decreased observing. Experiment 3 examined observing when a random-ratio schedule or a yoked random-time schedule of primary reinforcement was in effect across conditions. Removing the response requirement for the primary reinforcer increased observing, suggesting that the effects of the random-ratio schedule in Experiment 1 likely were due to an interaction between observing and responding for the primary reinforcer. In Experiment 4, decreasing the rate of primary reinforcement by increasing the duration of a random-time schedule decreased observing monotonically. Overall, these results suggest that observing decreases with decreases in the rate or magnitude of the primary reinforcer, but that behavior related to the primary reinforcer can affect observing and potentially affect measurement of conditioned reinforcing value.

Animals↗

PubMed2005

[Orbscan pachymetry: differences between observers when carrying out measurements of the corneal thickness].

PURPOSE: To study the corneal thickness and the inter-observer variability of corneal thickness measurements by means of Orbscan pachymetry. METHODS: We analysed the central and para-central corneal thickness of 30 subjects, whose age ranged from 19 to 38 years (mean 27.27, S.D. 5.25), with the Orbscan Topography System II (Orbscan, Inc., Salt Lake City, UT, USA). The mean of five consecutive measurements of the corneal thickness were obtained by two different observers and the results obtained were compared. RESULTS: No significant differences in mean corneal thickness between observers were found at central (p=0.749), nasal (p=0.931), supero-nasal (p=0.847), infero-nasal (p=0.930), temporal (p=0.918), supero-temporal (p=0.912) and infero-temporal (p=0.760) regions of the cornea. The maximum mean corneal thickness was found most commonly at the supero-nasal cornea (14 of 30 eyes for observer 1, and 16 of 30 eyes for observer 2). The difference between the central thickness and the maximum para-central thickness was 117 (S.D. 22) and 117 (S.D. 23) microns for observers 1 and 2 respectively (p=0.974). The difference between the central thickness and the minimum para-central thickness was 40 (S.D. 20) and 39 (S.D. 19) microns for observers 1 and 2 respectively (p=0.846). The difference between the minimum and the maximum para-central thickness was 76 (S.D. 24) and 77 (S.D. 23) microns for observers 1 and 2 respectively (p=0.895). CONCLUSIONS: Orbscan pachymetry allows central and para-central corneal studies to be carried out by different observers without any significant differences being found between them.

Adult↗

PubMed1995

HARBO, a simple computer-aided observation method for recording work postures.

OBJECTIVES: The aim of the study was to present an observation method focusing on the positions of the hands relative to the body and to evaluate whether this simple observation technique gives a reliable estimate of the total time spent in each of five work postures during one workday. METHODS: In the first part of the study the interobserver reliability of the observation method was tested with eight blue-collar workers. In the second part the observed time spent with work above the shoulder level was tested in relation to an upper-arm position analyzer, and observed time spent in work below knuckle level was tested in relation to a trunk flexion analyzer, both with 72 blue-collar workers. RESULTS: The interobserver reliability for full-day registrations was high. The intraclass correlation coefficients ranged from 0.99 to 1.00. The observed duration of work with hands above shoulder level correlated well with the measured duration of pronounced arm elevation (> 75 degrees). The product moment correlation coefficient was 0.97. The observed duration of work with hands below knuckle level correlated well with the measured duration of pronounced trunk flexion angles (> 40 degrees). The product moment correlation coefficient was 0.98. CONCLUSION: The present observation method, designed to make postural observations continuously for several hours, is easy to learn and seems reliable.

Adult↗

PubMedDate not supplied

[Observation, interview and discussion group: the silence of 3 research practices].

Before entering into the opposition between quantitative perspective and qualitative perspective of social research, the need is discussed of considering the social research process as a social process and the empirical observation situations per se as social situations. Therefore, in social research, the object of observation and the ways of observation are made in the same stuff. As in any social situation, social norms come into play in the observation situation. Thus, the article develops the presentation of three qualitative social research practices from their design as producing different social situations which, in turn, take on the nature of immediate contexts which favor respective articulations between the practical norms of specific social groups and the dominant social norms in society at large. The practices presented are: participant observation, in-depth interview and discussion group. A different articulation among social norms which finds silence to be privileged way of observation. Hence, the conclusion is reached that the management and analysis of silence is fundamental both for distinguishing the qualitative from the quantitative perspective, the former opening up more to silence than the latter, and to distinguish one practice from another, especially for observing the effects proper of the observation during the observation processes.

Group Processes↗

PubMed2005

Comparison of anatomical tibial plateau angle versus observer measurement from lateral radiographs in dogs.

This study was conducted to compare the anatomical tibial plateau angle (TPA) with that measured by observers from a lateral radiograph of the limb, the hypothesis being that there would not be any statistically significant differences between the observer measured TPA and the true anatomical TPA. Twelve pelvic limbs from skeletally mature greyhound cadavers, without any clinical or radiographic evidence of stifle pathology, were used in this study. The radiographs were taken of each limb in a lateral position with the primary beam centered over the tibial eminences and collimated to include the stifle and tarso-crural joints. For subsequent radiographs, Kirschner wires were inserted to enable identification of the tibial plateau. The TPA was then measured, by three observers, from the plain radiographs and by one observer from the marked radiographs. The mean observer TPA was 24.4 degrees (range 17-30 degrees) and the mean anatomical TPA was 23.8 degrees (range 15-31 degrees). The mean and median discrepancy between the anatomical TPA and the observer TPA was negative and very small (- 0.64 degrees and 0 degrees). The magnitude of the discrepancy between individual measurements made by the observers tended to overestimate small angles and underestimate the large ones, and this trend is statistically significant. These results suggest that the measurements made by observers accurately represent the anatomical slope of the tibial plateau. Therefore, observer TPA is suitable for the planning and assessment of TPLO procedures. However, as the anatomical TPA moves away from a median angle (23.25 degrees) the magnitude of error in the measurement increases.

Animals↗

PubMed1991

[Observer variation and accuracy in the clinical diagnosis of ascites].

Seventeen observers participated in an observer variation study of the clinical evaluation of ascites. In a blinded design, eight patients with diagnoses of liver disease were examined. Fourteen observers examined the patients twice in order also to estimate the intra-observer variation. The accuracy of the observers' statements was compared with ultrasound findings, by which mean ascites was demonstrated in two patients. Poor correspondance between the observers' gradings and volume estimations, and poor accuracy of the gradings, make qualitative and quantitative ascites estimations useless. The inter-observer agreement was found to be low although the intra-observer agreement was good. The observers' subjective certainty of correctness of their own findings, marked as certain/uncertain, did not reflect the chance of making a correct statement on each particular occasion. The individual patient's general ability of inducing certainty did relate the chance of forming a correct diagnosis. Ultrasonic investigation of the abdomen is recommended in all situations in which demonstration of ascites is essential to diagnosis or therapy.

Ascites↗

PubMed1990

Use of screening phase data to evaluate observer variation of sputum cytodiagnosis as an outcome measure in a chemoprevention trial.

Sputum samples obtained during the screening phase of a chemoprevention trial in heavy smokers were evaluated independently by trained cytotechnologists and classified for degree of cellular atypia according to the method of Saccommano et al. (G. Saccommano et al., Cancer (Phila.), 33: 256-270, 1974). The level of agreement within and between Observers A and B was calculated as the percentage of agreement and, in addition, a statistic was used (kappa) to correct for chance-expected agreement. Between observer agreement on 300 specimens from 130 subjects was 68% (204 of 300) (kappa = 0.58). Of the 96 disagreements, only 17 were of more than one category in the six-category classification. Within observer agreement for both Observers A and B was evaluated on a subset of 60 specimens from 49 subjects examined on two separate occasions by each observer. The percentage of within observer agreement was 80% for Observer A (kappa = 0.73) and 62% for Observer B (kappa = 0.49) (P less than 0.04). Altogether, 71% (25 of 35) of within observer discordant readings were confined to only one category. These data, obtained from the screening phase of the study, will allow us to refine the outcome measure for the trial without introducing bias that could result from knowledge of the actual study results. The failure of conventional cancer treatments to impact significantly on overall cancer mortality has led to an emphasis on prevention. If premalignant changes can be reliably detected at a time when the malignant process is reversible, then it may be feasible to intervene to prevent the occurrence of some cancers. The appropriate selection of subjects for such intervention trials and the subsequent demonstration of the efficacy of chemoprevention strategies are therefore crucial.

Etretinate↗

PubMed1998

Angiogenesis in breast cancer: a comparative study of the observer variability of methods for determining microvessel density.

The purpose of this study was to evaluate the reliability of different methods for estimating neovascularization in breast cancer and to compare them in terms of observer variability. The microvessel endothelium was stained immunohistochemically by antibodies against CD34. The investigated methods included Chalkley counting, estimation of intratumoral microvessel density (MVD) by one hot-spot, MVD by the mean value of three hot-spots, and the highest value of MVD in three hot-spots. In addition, we applied stereology in the quantification of angiogenesis in the whole tumor section by random and systematically distributed sampling fields. Each of forty tumors was measured with all methods, twice by the same observer and once by another observer. Observer variation was analyzed by orthogonal regression, estimating the slope and intercepts with 95% confidence intervals (CI), and by analysis of agreement using difference plots. Intraobservationally, the methods had variations of the same magnitude (coefficient of variation [CV] approximately 20%). Interobservationally, the stereologic estimate of vessel profiles, Q(A), from the whole tumor section and the Chalkley counting method had the lowest variation (CV approximately 21%), with a small contribution by observers alone (CV 8% to 9%). Interobservationally, the MVD methods had considerable variation with a large contribution by observers alone (CV approximately 30%), which was lowest using the mean of three hot-spots. Correlation slope and 95% CI of Chalkley were 1.18 (0.95, 1.48), CV 20%; slope of MVD (mean) was 1.14 (0.91, 1.43), CV 31%; and slope of MVD (max) was 1.15 (0.92, 1.45), CV 36%. The slope of MVD on one hot-spot was 1.33 (1.08, 1.63); CV 38%. Additional measurements performed using a conference microscope, eliminating subjectivity in hot-spot selection and field sampling, optimized the reproducibility: slope was 1.02 (0.99, 1.04); CV of differences, 3.5%. On the other hand, reproducibility was not necessarily optimized by choosing the same hot-spot area, because variation in selecting a microscopic field could yield different counting numbers. The stereologic estimation of QA based on the whole tumor section had a high reproducibility, with low variation due to observers. The Chalkley and MVD methods had moderate reproducibility, and the Chalkley method had low variation due to observers alone. For all methods, the biologic variation among patients was the major contributor to the total variation. The Chalkley and MVD methods have been published to provide significant prognostic estimates in breast cancer, but the Chalkley method has less observer variation and may be superior from a methodologic point of view.

Antigens, CD↗