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PubMed1999

[Precision and accuracy of white blood cell differentiation by an automated blood cell analyzer].

Precision and accuracy are important to assure the quality of clinical laboratory tests. We investigated the precision and accuracy of white blood cell (WBC) differentiation by automated blood cell analyzers. The coefficients of variation (CVs) of neutrophil, lymphocyte, monocyte, eosinophil and basophil differentiation by GEN.S (Coulter), based on a flow system and VCS technology, were 1.1%, 1.5%, 4.6%, 2.1%, and 33.3%, respectively. Between-run precision for neutrophil, lymphocyte, monocyte, eosinophil and basophil differentiation by GEN.S using cell control, 5C in 26 serial days was 2.0%, 2.8%, 6.5%, 9.2%, and 29.5%, respectively. The precision of WBC differentiation by blood cell analyzers based on the flow system was excellent except for basophil. We studied the accuracy of WBC differentiation by blood cell analyzers based on the flow system in contrast with eye-count. The correlations between neutrophil, lymphocyte, monocyte, eosinophil, and basophil percentages counted by GEN.S and by eye-count were r = 0.968, 0.971, 0.902, 0.940, and 0.391, respectively. The agreement rate between WBC differentiation by Microx, a blood cell analyzer based on pattern recognition, and eye-count cell by cell was good except for basophils. The accuracy of WBC differentiation by blood cell analyzers was also excellent excluding basophils.

Humans↗

PubMed1999

Accuracy of digitization using automated and manual methods.

BACKGROUND AND PURPOSE: Computerized 3-dimensional (3-D) motion measurement systems are used by those interested in human motion. The purposes of this study were (1) to determine the limits of accuracy in determining intersegmental angles during pendular motion at varying speeds and (2) to determine changes in accuracy introduced by autodigitization and digitization by experienced manual raters. METHODS: Angular speed of a T-shaped pendulum was systematically increased by releasing the pendulum from 4 angles (0 degrees [no movement], 45 degrees, 90 degrees, and 120 degrees). Twelve reference angles calculated from markers placed on the pendulum were estimated over 20 frames for 10 trials at each release position. RESULTS: Mean errors across trials and frames for intersegmental angles reconstructed by a 3-D motion measurement system were within +/- 1 degree across all release positions. An analysis of variance and a post hoc Tukey test revealed that the mean error for the autodigitized trials was larger than that for the manually digitized trials. For the autodigitized trials, the static trials (release position=0 degrees) produced less mean error than the trials with movement produced. The ICCs showed a high degree of consistency among all raters, ranging from .707 to .999. CONCLUSION AND DISCUSSION: Our findings support the conclusion that under carefully controlled conditions, a 3-D motion measurement system can produce clinically acceptable measurements of accuracy across a range of angular speeds. Furthermore, acceptable accuracy is possible regardless of the digitization method.

Gait↗

PubMed1999

Comparing the diagnostic accuracy of carbohydrate-deficient transferrin, gamma-glutamyltransferase, and mean cell volume in a general practice population.

In certain populations, the biological alcohol marker carbohydrate-deficient transferrin (CDT) is known to have a high diagnostic accuracy. The aim of this study was to compare the diagnostic accuracy of CDT, gamma-glutamyltransferase (gamma-GT), and mean cell volume (MCV) in a general practice population; more specifically, to ascertain whether CDT is a better tool than gamma-GT and MCV for (early) recognition of excessive alcohol use. To represent the general practice situation as realistically as possible, three different drinking patterns are defined: irregular excessive, regular excessive, and very excessive. From a sample of 524 men from seven general practices, sensitivity, specificity, and predictive values of the three markers for the three drinking patterns were compared, and receiver-operating characteristic analysis was used to compare differences between the markers. The results indicate that drinking patterns do influence the (difference in) diagnostic accuracy. CDT has a higher diagnostic accuracy for all three drinking patterns than gamma-GT and higher predictive values for hazardous [(ir)regular excessive] drinking patterns than MCV. However, receiver-operating characteristic analyses failed to demonstrate a significant difference between these patterns. It is concluded that the performance of all tests is too low to be useful for screening procedures in a general population; however, some tests may be useful for case finding. CDT seems to be the best alcohol marker available, although the difference between CDT and MCV is small.

Adolescent↗

PubMed1999

Reproducibility and accuracy of MR imaging of the brain after severe birth asphyxia.

BACKGROUND AND PURPOSE: MR imaging of the brain can be used to detect cerebral damage after suspected hypoxic-ischemic injury. This study examines the reproducibility and accuracy of MR imaging soon after severe birth asphyxia. METHODS: During a 48-month period, full-term newborn neonates, who died within the first week as a result of severe hypoxic ischemic encephalopathy, were included in the study if they had undergone early (<5 days old) MR imaging and postmortem neuropathologic studies. Two trained observers assessed reproducibility by examining multiple brain regions independently with current criteria and then defining and applying improved criteria. Accuracy of MR findings was tested by comparing the brain regions about which the two imaging raters agreed to those regions about which the two pathologists agreed. RESULTS: Eight neonates, with a median gestational age of 40 weeks (range, 38-40 weeks) and who suffered severe birth asphyxia, were included in the study. In the reproducibility study, MR imaging agreement was moderate when current criteria were used (k = .44). Using the improved criteria, agreement increased considerably (k = .62). Much of this improvement was due to limiting the analyses to the posterior limb of the internal capsule, thalamus, parietal cortex, hippocampus, and medulla. The posterior limb of the internal capsule was the most reliable region analyzed. MR imaging agreement was similar to that achieved by two experienced pathologists reviewing the histologic sections (k = .66). In the accuracy study, MR imaging abnormality was predictive of pathologic abnormality with a sensitivity of .79 and a positive predictive value of 1.0. The predictive value of a single MR imaging abnormality was .79 (95% confidence interval, .61-.96). CONCLUSION: Criteria that provide substantial reproducibility and accuracy for the interpretation of MR imaging findings very early after birth asphyxia can be derived.

Asphyxia Neonatorum↗

PubMed1999

Comparison of accuracy and cost effectiveness of clinical criteria and BUA for referral for BMD assessment by DXA in osteoporotic and osteopenic perimenopausal subjects.

A pilot study of 107 women aged 60-69 years recently suggested that the measurement of broadband ultrasound attenuation (BUA) provides a superior cost effective pre-screen referral method for bone mineral density (BMD) measurement by DXA (dual-energy X-ray absorptiometry) than can be achieved by clinical criteria (CC). The aim of this study was to compare the accuracy and cost effectiveness of BUA and clinical criteria in a younger cohort. 599 women aged 50-54 years (52.18 +/- 1.35) had previously been measured by DXA at lumbar spine and right femoral neck, along with BUA measurement of the right calcaneus. Each subject had also completed an extensive clinical and social questionnaire to ascertain those who would have met one or more of the six general clinical criteria adopted by our Centre. Each subject was classified by DXA using the WHO criteria as normal, osteopenic or osteoporotic, defined at lumbar spine or femoral neck. Sensitivity, specificity and accuracy were calculated for BUA and the clinical criteria, noting that analysis was undertaken with and without the oestrogen deficiency clinical criterion (CC1): "Any oestrogen deficient woman who would want to be treated or would want to continue treatment if found to be osteopenic or osteoporotic". The accuracy for identifying osteoporotic subjects was 72.8% for BUA (at the point of matched sensitivity and specificity, 75 dB MHz(-1)), 30.7% for CC(1-6) and 64.3% for CC(2-6). When osteopenic subjects were incorporated, the accuracies were 63.8% for BUA (at the point of matched sensitivity and specificity, 82 dB MHz(-1)), 60.3% for CC(1-6) and 55.7% for CC(2-6). The minimum cost per osteoporotic subject correctly identified was pound sterling 573.50 by DXA alone, pound sterling 325 by BUA, pound sterling 458 by CC(1-6) and pound sterling 416 by CC(2-6). When osteopenic subjects were incorporated, the costs were pound sterling 87, pound sterling 83.50, pound sterling 78 and pound sterling 74, respectively. The overall cost, dependent upon the prevalence of osteoporosis (or osteopenia) within the population, more accurately indicates the feasibility of a population-based screening programme. For the identification of either osteoporotic or osteopenic subjects from the general population by DXA, the prevalence-compensated cost (cost per subject correctly identified multiplied by prevalence) is pound sterling 45, irrespective of age cohort. If CC(2-6) were adopted for the identification of osteoporotic subjects alone, the prevalence-compensated cost would be pound sterling 32 and pound sterling 42 for the 50-54 and 60-69 aged cohorts, respectively. For BUA, the prevalence-compensated cost falls to pound sterling 25 and pound sterling 43 for the 50-54 and 60-69 aged cohorts, respectively. If osteoporotic or osteopenic subjects were to be identified in the 50-54 aged cohort, both CC(2-6) (pound sterling 38) and BUA (pound sterling 43) perform similarly to DXA alone. BUA appears to provide a valuable population pre-screen for the identification of osteoporotic subjects, less so for osteopenic. It is suggested that if both osteopenic and osteoporotic women are to be identified for clinical management incorporating DXA, then neither BUA nor clinical criteria are satisfactory referral methods. An unanswered question from this study, however, is whether ultrasound has an independent role in the assessment of fracture risk for perimenopausal women who do not have the benefit of referral for DXA.

Absorptiometry, Photon↗

PubMed1999

Influence of catheter position and equipment-related factors on the accuracy of intravascular ultrasound measurements.

BACKGROUND: Intravascular ultrasound (IVUS) is frequently used as an adjunct to coronary angiography to guide revascularization procedures and, more recently, to estimate atherosclerotic plaque volumes. Although accuracy of IVUS imaging and analysis is crucial for these measurements, available data are scarce. The purpose of this in vitro study is to determine the extent to which transducer position and equipment-related factors influence measurement accuracy. METHODS: Cross-sectional views of tubular vessel phantoms (diameter 2-14 mm) were acquired using 3.2 French catheters in coaxially centered, eccentric and oblique positions. Catheters were sequentially connected to two different ultrasound systems (A and B) to estimate equipment-related variability. In system B, two software versions were used to analyze ultrasound images. Longitudinal views of phantom segments were reconstructed to document transducer misplacement. RESULTS: Oblique transducer positioning resulted in a non-linear overestimation of phantom areas that was independent of lumen size and also resulted in dramatic distortions of three-dimensionally reconstructed phantom geometry. Eccentric positioning did not significantly influence measurement accuracy. In coaxial positioning, differences between measured and true areas increased non-linearly from 0.36 to 4.5 mm2 in system B and in a linear fashion from -0.01 to 2.68 mm2 in system A with increasing phantom diameters. Relative differences decreased from 11.4% to 2.9% with increasing reference areas in system B (positive off-set error). When using updated software in system B, the off-set error was negative and relative error diminished from -1.34% to 0.44% with increasing phantom size. CONCLUSION: Transducer position and equipment-related factors influence the accuracy of intravascular ultrasound, which may lead to misinterpretation of vessel size and geometry even in straight vessel segments. Transducer position may be controlled by the reconstruction of longitudinal images. Ultrasound equipment should be calibrated before using it for quantitative measurements.

Cardiac Catheterization↗

PubMed2000

In vitro evaluation of the accuracy of open-configuration MRI in endovascular techniques.

The purpose of this study was to determine the accuracy of an interventional magnetic resonance imaging (iMRI) system to position an endovascular catheter in an in vitro model that simulated an infrarenal aortic aneurysm. Adequate visualization of abdominal aortic aneurysms (AAAs) was shown previously in humans. A dedicated near-real-time imaging protocol readily available on a Signa SP 0.5T open configuration MRI unit (General Electric Medical Systems, Milwaukee, WI, USA) was used to image the AAAs of ten human volunteers. A pulsatile in vitro model that simulated an AAA was built, which included the kidneys, the renal arteries, the aorta, and the iliac arteries. A catheter was advanced to a predetermined target through one of the iliac limbs of the model. Using two different techniques, the accuracy with which an interventionist could position the endovascular catheter under the near-real-time guidance of the iMRI system was evaluated. The AAAs of all ten patients were visualized, including the aneurysm wall, the thrombus within it, and the residual lumen, while maintaining adequate contrast, signal, and imaging speed. The position of the catheter was evaluated on target in 42 in vitro procedures. This series of tests showed an average accuracy of 1 mm for catheter positioning. The near-real-time imaging mode of the iMRI system enabled satisfactory evaluation of human AAAs, and it showed great accuracy for catheter positioning in the in vitro model. These results provide optimism regarding the potential of iMRI in endovascular surgery.

Aortic Aneurysm, Abdominal↗

PubMed2000

Accuracy of 131I tumor quantification in radioimmunotherapy using SPECT imaging with an ultra-high-energy collimator: Monte Carlo study.

UNLABELLED: Accuracy of 131I tumor quantification after radioimmunotherapy (RIT) was investigated for SPECT imaging with an ultra-high-energy (UHE) collimator designed for imaging 511-keV photons. METHODS: First, measurements and Monte Carlo simulations were carried out to compare the UHE collimator with a conventionally used, high-energy collimator. On the basis of this comparison, the UHE collimator was selected for this investigation, which was carried out by simulation of spherical tumors in a phantom. Reconstruction was by an expectation-maximization algorithm that included scatter and attenuation correction. Keeping the tumor activity constant, simulations were carried out to assess how volume-of-interest (VOI) counts vary with background activity, radius of rotation (ROR), tumor location, and size. The constant calibration factor for quantification was determined from VOI counts corresponding to a 3.63-cm-radius sphere of known activity. Tight VOIs corresponding to the physical size of the spheres or tumors were used. RESULTS: Use of the UHE collimator resulted in a large reduction in 131I penetration, which is especially significant in RIT where background uptake is high. With the UHE collimator, typical patient images showed an improvement in contrast. Considering the desired geometric events, sensitivity was reduced, but only by a factor of 1.6. Simulation results for a 3.63-cm-radius tumor showed that VOI counts vary with background, location, and ROR by less than 3.2%, 3%, and 5.3%, respectively. The variation with tumor size was more significant and was a function of the background. Good quantification accuracy (<6.5% error) was achieved when tumor size was the same as the sphere size used in the calibration, irrespective of the other parameters. For smaller tumors, activities were underestimated by up to -15% for the 2.88-cm-radius sphere, -23% for the 2.29-cm-radius sphere, and -47% for the 1.68-cm-radius sphere. CONCLUSION: Reasonable accuracy can be achieved for VOI quantification of 131I using SPECT with an UHE collimator and a constant calibration factor. Difference in tumor size relative to the size of the calibration sphere had the biggest effect on accuracy, and recovery coefficients are needed to improve quantification of small tumors.

Algorithms↗

PubMed2000

Objectivity and accuracy of mammogram interpretation using the BI-RADS final assessment categories in 40- to 49-year-old women.

To determine if use of the five final assessment categories of the American College of Radiology's Breast Imaging Reporting and Data System (BI-RADS) improved objectivity or accuracy of mammographic evaluation in 40- to 49-year-old women, fifty mammograms of 40- to 49-year-old women that were obtained at a tertiary referral teaching hospital were classified according to those five final assessment categories. The mammograms were blinded to six American Osteopathic Board of Radiology-certified radiologists who were asked to classify each mammogram within the five final BI-RADS categories based on the mediolateral oblique and craniocaudal views presented. No history was allowed. Use of the BI-RADS five final assessment categories provided moderate interobserver objectivity, moderately high agreement among the radiologists' interpretation (reliability), and moderate accuracy of interpretation (validity) when compared to criterion. Moderate interobserver reliability and accuracy has been previously identified; however, no scientific review of the BI-RADS five final assessment categories in 40- to 49-year-old females was discovered in the current literature. No overall improvement of objectivity or accuracy was demonstrated using the five final assessment categories of the BI-RADS lexicon in 40- to 49-year-old women.

Adult↗

PubMed2000

Diagnostic accuracy of 99mTc-sestamibi breast imaging: multicenter trial results.

UNLABELLED: Although mammography is well established as a first-line tool for breast cancer screening and detection, efforts to develop complementary procedures continue. Observation of 99mTc-sestamibi tumor uptake provided the impetus for its evaluation as an adjunctive technique. This trial's objectives were to determine in a multicenter trial the diagnostic accuracy of 99mTc-sestamibi in women with suspected breast cancer and to investigate factors influencing diagnostic accuracy. METHODS: Our multicenter trial enrolled 673 women (387 with nonpalpable abnormalities; 286 with palpable abnormalities) scheduled for excisional biopsy or mastectomy. Blinded and unblinded interpretations of scintigraphic images were compared with core laboratory established histopathologic diagnoses to define the diagnostic accuracy of 99mTc-sestamibi breast imaging. RESULTS: Blinded readers' diagnostic accuracy was 78%-81%. Inter-reader agreement was excellent, ranging from 95% to 100% (kappa = 0.82-0.99). Overall institutional sensitivity and specificity for 99mTc-sestamibi breast imaging were 75.4% and 82.7%, respectively. In this population with a 40.1% disease prevalence, the positive predictive value was 74.5% and the negative predictive value was 83.4%. The negative predictive value was 94% in patients with a 40% or lower mammographic likelihood of breast cancer. Sensitivity was higher for palpable abnormalities; specificity was higher for nonpalpable abnormalities. Sensitivity was decreased for tumors <1 cm in largest dimension but appeared not to be affected by patient's age. CONCLUSION: As an adjunct to current procedures, 99mTc-sestamibi breast imaging may contribute to patient management decisions in selected populations, including women with dense breasts, mammographically indeterminate lesions >1 cm, and palpable abnormalities.

Biopsy↗

PubMed2000

Effect of 3 medicaments on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions.

OBJECTIVE: The purpose of this study was to determine the effect of retraction cord medicaments (aluminum chloride, ferric sulfate, and ferric subsulfate/ferric sulfate) on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions. METHOD AND MATERIALS: Polyvinyl siloxane impressions were made of standardized metal dies (American Dental Association [ADA] specification No. 19) treated with 1 of the 3 retraction cord medicaments. Dimensional accuracy was evaluated by comparing the average length of a line in the impressions to the standard die. Surface detail reproduction was evaluated by viewing the impressions under low-angle illumination at x10 magnification. Reproduction was considered satisfactory if 2 of 3 horizontal lines were reproduced continuously. The dies were also evaluated under the microscope before the impression was made. RESULTS: The medicaments did not significantly effect the dimensional accuracy; mean shrinkage was within ADA guidelines in the treatment groups. All of the medicaments had an adverse effect on surface detail reproduction. These effects were statistically significant compared to the untreated control. CONCLUSION: Although the changes in dimensional accuracy were within ADA guidelines, the surface detail reproduction was modified such that the impression would be considered clinically unacceptable. For optimal results, care must taken to remove all traces of these retraction cord medicaments prior to recording of a polyvinyl siloxane impression.

Aluminum Chloride↗

PubMedDate not supplied

[A model for evaluating internal accuracy].

OBJECTIVE: To provide an evaluation model of internal accuracy illustrating its use in a quality control program of clinical chemistry. METHODS: The model uses data transformed to percentage of assigned value (%AV) that allows the pooling of different controls. Precision is evaluated by the mean of the intracontrol coefficients of variation, and accuracy by the mean of means of the %VAs and its standard deviation. The model was used in 17,280 measurements of 23 analytes assayed in seven pairs of controls (medium and high concentration) during four years in two automated clinical chemistry analyzers. RESULTS: The model established inaccuracy of 5% to 25% in seven analytes, five of them enzymes. It also detected interanalyzer differences in accuracy of five analytes (22%) and an erroneous assigned value in 19 of 304 controls (6%). CONCLUSIONS: The model showed its capacity to dissect the sources of variation of accuracy. There was inaccuracy in 30% of the analytes but further studies are needed to validate these inaccuracies with controls of other sources. The model can be useful for control programs of any quantitative assay system. A summary description of the model's operation is given.

Chemistry, Clinical↗

PubMed2001

[Diagnostic accuracy of the percutaneous spinal biopsy. Optimization of the technique].

Between 1992 and 1999, 210 percutaneous biopsies of the spine were performed in our department of neuroradiology. The purpose of this retrospective study was to determinate the diagnostic accuracy of the procedure and to discuss the technical points that might improve its accuracy. An accurate diagnosis was obtained in 72% of the spondylodiscitis and in 80% of the tumoral lesions (88% of metastatic lesions and 68% of primary tumors). These results have been compared with the other results of the literature. There was no significant difference of accuracy between CT and fluoroscopic guided biopsies. On the other hand, the type of needle and the multiplicity of samples for bacteriological and histologic studies improve the diagnostic accuracy.

Adolescent↗

PubMedDate not supplied

Evaluation of clinical thermometers for accuracy and reliability.

The purpose of this study was to examine the accuracy and reliability of a wide range of clinical thermometry instruments and technologies. In a historical sense, the purpose of this study was to determine if the improvements in speed, ease of use, and safety realized in the last 100 years have been offset by a loss of accuracy and/or reliability. In view of current events, the purpose was to determine if the new generation of electronic, digital clinical thermometers could be used to replace the traditional glass/mercury thermometers. Nine clinical thermometers representing electronic, digital oral, and predictive oral; electronic, digital infrared tympanic; and liquid crystal urinary technologies were evaluated. Accuracy was determined by comparing the temperatures obtained from these test instruments with those of the reference, glass/mercury oral thermometer. Reliability was determined by test-retest evaluation. All of the thermometers evaluated were significantly less accurate when compared with the reference thermometer in this study. All of the test instruments significantly underestimated higher temperatures and overestimated lower temperatures. This study indicated that the improvements in safety, speed, and ease of use of the newer clinical thermometers have been offset by a loss in accuracy and reliability. It also indicated that the current generation of electronic, digital clinical thermometers, in general, may not be sufficiently accurate or reliable to replace the traditional glass/mercury thermometers.

Adult↗

PubMed2001

The accuracy and interobserver reproducibility of endometrial dating.

Although controversial, diagnosis of luteal phase defect (LPD) includes the morphological assessment of endometrial development. This study was conducted to determine if refresher training in the histological criteria could improve the accuracy and interobserver reproducibility of endometrial dating. Seventy-eight endometrial biopsies were dated by a reference panel of two pathologists and then reviewed twice by a study panel of four pathologists. In the first review, usual practice was applied. Prior to the second review, they studied a standard document of histological criteria. Samples were dated as proliferative, secretory (post-ovulatory day, POD), menstrual, and undatable. Accuracy levels based on the reference dating and agreement levels using kappa values were calculated per review and compared. The kappa for overall dating was 0.683 in the first review and 0.696 in the second. The respective first and second review kappa values were 0.736 and 0.771 for proliferative, and 0.794 and 0.764 for secretory. Amongst those dated as secretory in the first and second reviews, respectively, 31 and 28% were assigned the same POD by any two panellists, 68 and 63% were dated to within 1 day, and 77 and 71% were dated to within 2 days. Accuracy levels per panellist for overall dating were very high in both reviews but were low for individual PODs. Accuracy and interobserver reproducibility were unaffected by refresher training, suggesting the limits of histological dating have been reached.

Biopsy↗

PubMed2001

Reliability of a 5-min running field test and its accuracy in VO2max evaluation.

BACKGROUND: Five-min running field test (5_RFT) was established for determining individuals' maximal aerobic velocity (V(amax)) and functional aerobic capacity (VO2peak) during horizontal run. We determined the number of trials required for establishing high reliability of the 5_RFT and examined its accuracy in evaluating individuals' maximal aerobic capacity (VO2max). METHODS: The V(amax)(5) recorded during the 5_RFT on four separate days was compared in 45 subjects (14 male, 31 female, 17.0+/-0.2 yrs) of various levels of physical fitness. The accuracy of VO2max evaluation using V(amax)(5) was examined via regression analysis in additional 23 male subjects (20.7+/-0.3 yrs). RESULTS: The mean correlation coefficient of V(amax)(5) among four trials was 0.94. Intraclass reliability coefficient across all trials was 0.98. For trial 3 and 4, the mean value of subjects' V(amax)(5) was higher than that of trial 1 and 2. V(amax)(5) of trial 2 was also higher than that of trial 1 while no difference was found between trial 3 and 4. F-test of equality of variances demonstrated similar sample variance of V(amax)(5) in all trials. Within-subject coefficient of variation in V(amax)(5) was 3.7 percent for all trials was reduced to 2.4 percent for trial 3 vs 4. For examining the accuracy in VO2max evaluation, regression analysis revealed that the V(amax)(5) explained 35.0 percent of the variance of measured VO2max (SEE = 5.64 ml x kg(-1) x min(-1)). CONCLUSIONS: The 5_RFT is reliable in determining V(amax)(5). Nevertheless, two familiarization sessions are recommended for achieving the best performance in the test. The 5_RFT cannot evaluate VO2max with reasonable accuracy in young males.

Adolescent↗

PubMed2001

Automatic identification of patients eligible for a pneumonia guideline: comparing the diagnostic accuracy of two decision support models.

BACKGROUND: In busy clinical settings, physicians often do not have enough time to identify patients for specific therapeutic guidelines. As a solution, decision support systems could automatically identify eligible patients and trigger computerized guidelines for specific diseases. Applying this idea to community-acquired pneumonia (CAP), we developed a Bayesian network (BN) and an artificial neural network (ANN) for identifying patients who have CAP and are eligible for a pneumonia guideline. OBJECTIVE: The aim of this study was to determine whether the diagnostic accuracy of these two decision support models differs in terms of identifying CAP patients. METHODS: We trained and tested the networks with a data set of 32,662 adult patients. For each network, we (1) calculated the specificity, the positive predictive value (PPV), and the negative predictive value (NPV) at a sensitivity of 95%, and (2) determined the area under the receiver operating characteristic curve (AUC) as a measure of overall accuracy. We tested for statistical difference between the AUCs using the correlated area z statistic. RESULTS: At a sensitivity of 95%, the respective values for specificity, PPV, and NPV were: 92.3%, 15.1%, and 99.9% for the BN, and 94.0%, 18.6%, and 99.9% for the ANN. The BN had an AUC of 0.9795 (95% CI: 0.9736, 0.9843), and the ANN had an AUC of 0.9855 (95% CI: 0.9805, 0.9894). The difference between the AUCs was statistically significant (p=0.0044). CONCLUSIONS: The networks achieved high overall accuracies on the testing data set. Because the difference in accuracies is statistically significant but not clinically significant, both networks are equally suited to drive a guideline.

Area Under Curve↗

PubMed2002

Nurses' accuracy in estimating backrest elevation.

BACKGROUND: Positioning patients is a key component of nursing care and can affect their morbidity and mortality. The Centers for Disease Control and Prevention recommend that patients receiving mechanical ventilation have the head of the bed elevated 30 degrees to 45 degrees to prevent nosocomial pneumonia. However, use of higher backrest positions for critically ill patients is not common nursing practice. Backrest elevation may be affected by the accuracy of nurses' estimates of patients' positions. OBJECTIVES: To determine the difference between nurses' estimates of bed angles and measured bed angles and to describe the relationship between nurses' characteristics and the accuracy of their estimates. METHODS: A convenience sample of 67 nurses attending the 1999 American Association of Critical-Care Nurses National Teaching Institute and Critical Care Exposition in New Orleans, La. Each subject provided demographic information and estimated 3 bed angles. The angles were preselected by using a random number table. Summary statistics were used and were categorized according to the demographic information provided by participants. Estimated angles were correlated with measured angles, and accuracies in estimating angles were correlated with demographic characteristics. RESULTS: Nurses were accurate in estimating bed angles (correlation, 0.8488). Demographic information, including sex, age, years of practice, years of critical care practice, basic education, highest educational level, and present position had no relationship to accuracy. CONCLUSIONS: Nurses are able to estimate backrest elevation accurately. Other explanations are needed to understand why recommendations for backrest elevation are not used in practice.

Adult↗