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PubMed1996

Reappraisal of quantitative esophageal scintigraphy by optimizing results with ROC analyses.

UNLABELLED: This study investigates whether systematic analyses of methodological issues contribute to improve and renew the diagnostic role of quantitate esophageal scintigraphy. METHODS: Forty-seven patients with normal (n = 26) and pathologic (n = 21) esophageal function were studied with scintigraphy and manometry, using the latter findings as the gold standard. Scintigraphic data were analyzed by receiver operator characteristic (ROC) methods to: establish the optimal decision threshold for six different quantitative parameters, evaluate their inherent discrimination capacity and compare liquid compared with solid bolus data. RESULTS: Quantitative parameters have shown remarkable differences in their potential to discriminate between normal and pathologic findings (percentage of emptying at definite time points > mean time > transit time > mean transit time > Tmax). Sensitivity of 95% at a specificity of 96% was the optimum obtained. At comparable specificity levels, solid bolus studies generally demonstrated higher sensitivity than liquid bolus studies. CONCLUSION: The diagnostic performance of optimized esophageal scintigraphy is close to that of manometry. Our findings do not only renew the role of esophageal scintigraphy as an accurate screening test for esophageal motility disorders but also invalidate recent reservations about the diagnostic potential of this method.

Adult↗
PubMed1979

[Nutritional requirements and parenteral feeding].

1. The nutritional needs of man are governed by the law of the minimum (structural and protective substances) and the isodynamic rule (exchangeability of various energy carriers) There is a tendency to abandon the traditional concept of requirement as an absolute value (g or mg/day) and replace it by 3 graded parameters (minimal - lowest acceptable - desirable supply). Today nutrient density is of utmost importance in the planning and evaluation of food formulas, i.e. the content per 1000 kcal or per MJ = mega-Joule. 2. The metabolism of nutrients proceeds (simplified) in 3 phases: a) digestion (comminution); b) coordination and conversion in intermediary metabolism; c) direct use in synthetic or oxidation processes. This creates problems of balance, of co-ordination and regulation. In the phases b and c the same conformities apply for oral and parenteral feeding. 3. Particular features of parenteral feeding: Exclusion of intestinal flora, limited capacity of uptake by the circulation and, especially, the lowered capacity of biochemical regulatory mechanisms (homeostasis) in patients requiring parenteral feeding necessitate optimal coordination of supply and effective needs. Attempts to comply are made by continuous infusions, diversification of the substrate supply and optimisation of the different components. In principle, priority is given to those nutritional factors which promote anabolism (tissue formation) and counteract catabolism (tissue breakdown). 4. Example: protein needs. --Recapitulation of quantitative and qualitative requirements regarding protein and amino acid supply. --Discussion of the different recommendations and guidelines. --Discussion of the criteria for evaluation and the composition of an optimal amino acid mixture (nitrogen balance and growth as criteria). 5. Conclusions for parenteral feeding. The supply of amino acids should be on the generous side because there is an increased requirement in the "acute phase" and in convalescence. The amino acid composition should correspond to the pattern of a high quality food protein. The E/T ratio (essential AS versus total AS supply) is an indicator. The value proposed as a guideline is E/T approximately 3. However, an exaggerated amino acid cosmetic is not recommended. 6. Diagnostic problems. In the interest of optimal results of treatment, foremost attention should be given to the detection of latent deficiency states and the improvement of nutrition at large. The list of indicators given in the figures should be consulted whenever there is evidence of undersupply. The so-called "hospital malnutrition", as described in recent studies, should obviously not occur.

Amino Acids↗
PubMed1996

Use of neural networks to diagnose acute myocardial infarction. I. Methodology.

We investigated several aspects of using neural networks as a diagnostic tool: the design of an optimal network, the amount of patients' data needed to train the network, the question of training the network optimally while avoiding overfitting, and the influence of redundant variables. The specific clinical problem chosen for illustration was the diagnosis of acute myocardial infarction, given only the electrocardiogram and the concentration of potassium in serum at the time of admission. We found that, in contrast to usual practice, the termination of the training process should be based on the generalization performance and not on the training performance. We also found that a principal component analysis can be used to eliminate redundant variables, thereby reducing the data space. The diagnostic performance of the neural network we used was 78%--superior to that of linear discriminant function analysis but similar to that of quadratic discriminant function analysis.

Diagnosis, Computer-Assisted↗
PubMed2006

A quadratic model for combining quantitative diagnostic assessments from radiologist and computer in computer-aided diagnosis.

RATIONALE AND OBJECTIVES: Some computer-aided diagnosis (CAD) methods produce a quantitative diagnostic assessment (eg, likelihood of malignancy) based on computer image analysis that a radiologist who uses the computer aid must combine with his or her own assessment. Observer studies show that although CAD helps radiologists improve diagnostic performance, ad hoc use of computer aid can produce performance inferior to that of computer alone, indicating that radiologists are unable to incorporate computer assessment optimally into their final assessment. We describe a mathematical model for combining two correlated diagnostic assessments that may provide a basis for merging radiologists' ratings with computer assessments in a way that yields greater diagnostic accuracy than ad hoc merging by radiologists. MATERIALS AND METHODS: We calculate a likelihood ratio from the bivariate binormal model that describes joint probability density functions of latent decision variables of two correlated diagnostic assessments. To the extent that the bivariate binormal model is valid and that the model's parameters can be estimated reliably, results obtained in this way will be optimal because the likelihood ratio is the decision variable used by the ideal observer in any two-group classification task. We evaluated this method on two observer study datasets and in Monte Carlo simulations. RESULTS: This method produced better performance than achieved by radiologists when they incorporated computer assessment in an ad hoc way. Simulations show that with a large number of cases, this method can produce results indistinguishable from the ideal observer performance. CONCLUSIONS: This method can potentially help radiologists use quantitative computed diagnostic assessments optimally, thereby surpassing the computer in accuracy.

Analysis of Variance↗
PubMed1978

Operative fluoroscopy and cholangiography. The use of modern radiologic technics during surgery.

Operative cholangiography as currently performed in many hospitals in the United States may be a cumbersome procedure yielding less than optimal information. For maximal accuracy and diagnostic yield, operative radiographic examination of the biliary tract should include fluoroscopic observation and aimed spot films. The advantages gained by using modern radiologic equipment and technics are increased image clarity, increased capability for functional assessment of a dynamic system, increased efficiency, and decreased radiation hazard. In a series of 100 patients undergoing operative cholangiography by our technic, only one retained stone was demonstrated by postoperative studies. Five anomalies of the ductal system were easily identified and possible injury to the anomalous ducts averted. Considering the morbidity and mortality attendant upon inadequate or inappropriate biliary tract operations, investment in the sophisticated equipment necessary for optimal operative radiography is small indeed.

Biliary Tract Surgical Procedures↗
PubMed1989

Evaluation of multivalent Leptospira fluorescent antibody conjugates for general diagnostic use.

Four lots of conjugate were evaluated for optimal dilution and degree of fluorescence produced with reference cultures and bovine and porcine leptospira isolates. One lot that uniformly produced better fluorescence was evaluated for sensitivity and specificity with reference cultures, isolates, culture-positive tissues, and 13 other bacterial species. Further evaluation of the conjugates was done with bovine, porcine, and ovine specimens submitted to a diagnostic laboratory. Leptospires were detected with the fluorescent antibody test (FAT) in 9 of 21 culture-positive bovine kidneys and were detected in diluted cultures when present at concentrations of 10(2)-10(3) organisms/ml. With the exception of Treponema hyodysenteriae, FAT's of other bacterial cultures produced minimal fluorescence or were negative. Positives were characterized by moderate to brilliant fluorescence of typical cell forms, and most nonspecific fluorescence was eliminated with a flazo-orange counterstain. The results indicated that the FAT utilizing multivalent conjugates could be used successfully as an additional method for diagnosis of leptospira infections.

Animals↗
PubMed2003

New findings on alternative criteria for PTSD in preschool children.

OBJECTIVE: An alternative set of criteria for posttraumatic stress disorder (PTSD) for preschool children was analyzed for validity. METHOD: Sixty-two traumatized children and 63 healthy controls, aged 20 months through 6 years, were assessed. The traumatic experiences included motor vehicle collisions, accidental injuries, abuse, and witnessing violence. The number of symptoms required for clusters C and D and the utility of proposed symptoms were systematically analyzed. RESULTS: No cases met the DSM-IV algorithm for PTSD. Cluster B was endorsed 67.9% of the time. The proportion of cases meeting the cluster C threshold was 2% when three symptoms were required, 11% when two symptoms were required, and 39% when one symptom was required. The rate of cluster D was 45% when two symptoms were required and 73% when one symptom was required. Four novel symptoms did not substantially add to the diagnostic validity of the criteria. The optimal algorithm (one cluster B symptom, one cluster C symptom, and two cluster D symptoms) diagnosed PTSD at a rate of 26%. Measures of comorbid symptoms concurrently provided convergent validation to support this revised algorithm. CONCLUSION: Revisions to the DSM-IV PTSD criteria continue to be supported so that highly symptomatic young children can be diagnosed.

Algorithms↗
PubMed1986

Clinically expedient reporting of rapid diagnostic test information.

With the development of rapid diagnostic tests in the clinical microbiology laboratory has come an awareness of the importance of rapid results reporting. Clearly, the potential clinical impact of rapid diagnostic tests is dependent on expeditious reporting. Traditional manual reporting systems are encumbered by the necessity of transcription of test information onto hard copy reports and then the subsequent distribution of such reports into the hands of the user. Laboratory computers when linked directly to CRTs located in nursing stations, ambulatory clinics, or physician's offices, both inside and outside of the hospital, permit essentially instantaneous transfer of test results from the laboratory to the clinician. Computer-assisted results reporting, while representing a significant advance over manual reporting systems is not, however, without problems. Concerns include validation of test information, authorization of users with access to test information, mechanical integrity, and cost. These issues notwithstanding, computerized results reporting will undoubtedly play a central role in optimizing the clinical impact of rapid diagnostic tests.

Clinical Laboratory Techniques↗
PubMed2004

Cardiovascular and renal risk assessment as a guide for treatment in primary hypertension.

BP levels per se may be an unreliable indicator of risk in the individual patient. In fact, the global cardiovascular profile, including the presence and degree of target organ damage, is a better predictor of future events and, therefore, should be used to choose both treatment and BP goals. However, the prevalence of target organ damage and therefore the percentage of patients who are at risk very much depends on the diagnostic techniques used. However, as a result of the high prevalence of hypertension and its financial impact on public health systems, limiting unnecessary and extensive diagnostic tests also should be a priority. The routine search for microalbuminuria may lead to the detection of a significantly greater percentage of patients who are at high risk while contributing the optimization of the cost-effectiveness of diagnostic workup in hypertensive patients.

Albuminuria↗
PubMed1997

Iopentol (Imagopaque 300) compared with iopromide (Ultravist 300) in abdominal CT. A multi-centre monitoring trial assessing adverse events and diagnostic information--results from 518 patients in Spain.

OBJECTIVES: Iopentol (Nycomed Imaging AS, Oslo, Norway) and iopromide (Schering AG, Berlin, Germany) are low-osmolar, non-ionic, iodinated contrast media (CM) used in abdominal CT examinations. The intravenous safety profile and radiological efficacy of iopentol and iopromide were studied in 518 patients. Specifically, frequency of adverse events (AEs), subjective change in quality of diagnostic information, and quantitative enhancement characteristics were compared. MATERIALS AND METHODS: A prospective, double-blind, randomized, multicentre, parallel-group study was conducted at 8 hospitals. Patients received 100 ml of either iopentol 300 mg I/ml or iopromide 300 mg I/ml. RESULTS: The incidence of patients with AEs was statistically significantly lower in the iopentol group compared to the iopromide group (2.3% vs. 8.9%, p < 0.001). Discomfort was frequent in both groups (44.8% vs. 49.4%, p = 0.33), sensation of heat and warmth being most common. Overall, diagnostic information was similar in both groups. Both CM gave high percentages of examinations rated as optimal (87.1% vs. 90.5%, p = 0.34) and in which diagnostic confidence was increased (87.5% vs. 91.1%, p = 0.22). No significant differences between the two CM were found concerning quantitative enhancement characteristics. CONCLUSIONS: In this study iopentol was significantly safer than iopromide for contrast enhanced CT examination of the abdomen. Radiological efficacy was similar with both CM.

Contrast Media↗
PubMedDate not supplied

[Standardization and its importance in rendering medical care to patients with cancer of the bladder].

There are only as many as 31 specialized oncourological departments in 24 of 89 (27%) Federation Subjects in the Russian Federation that can render the oncourological care at the municipal and federal levels. As for other remaining 65 (73%) Subjects, the urologists are preoccupied with diagnosis and treatment of urinary-bladder cancer in them. Russian patient-care facilities have presently differing opportunities in the sphere of diagnosis and treatment of the mentioned pathology. Their related outfit for this purpose is on the whole unsatisfactory. An optimal management of medical care rendered to the discussed category of patients and targeted at promoting its quality and efficiency is possible only on the basis of standardization of diagnostic and treatment approaches. The stage-nature of medical care rendered to such patients is closely related the standardization issues. An accurate definition of stages and of patient-care facilities, which would be in charge for the above stages, would, in the end, clearly depict a sequence of steps for the diagnostic-and-therapeutic schemes applicable to patients with cancer of the urinary bladder. This, in its turn, would optimize the diagnostic-and-therapeutic process and outline the priority spheres in healthcare financing.

Cancer Care Facilities↗
PubMed2004

[Patient dose evaluation and optimization of uropoietic multiphasic multislice CT examination].

PURPOSE: The aim of this study was to optimize acquisition data during multislice multiphasic CT examination of the renal excretory system in order to reduce patient effective dose without deterioration of the imaging quality. MATERIALS AND METHODS: With the aid of two dedicated software programmes we evaluated the patient effective dose during both multislice multiphasic CT examination of the renal excretory system and excretory urography. With the CT acquisition protocol, images of a test object (Helical CT phantom, CIRS) were examined by two expert radiologists to assess the number of visible inserted test images. Other scans of the test object were then obtained utilizing decreased tube current intensity; among these that with minor information loss was identified. Patient effective dose was measured utilizing correspondent acquisition data. RESULTS: Patient effective dose during multiphasic multislice CT examination before optimization (280 mA tube current intensity) was 22.9 mSv for males and 31.1 mSv for females; after optimization it was 19.6 mSv and 26.7 mSv, respectively, with a 14% decrease. Patient effective dose during CT direct phase before optimization was 8.9 mSv for males and 12.8 mSv for females, after optimization 7.6 mSv and 11 mSv with a 15% decrease. The absorbed dose for males is lower because the females gonads are completely included in the primary CT beam, whereas the testicles are hit by diffuse radiation only. DISCUSSION AND CONCLUSIONS: During CT direct phase the patient absorbed dose is 1.45 for males and 1.9 for females (1.2 and 1.6 respectively after optimization) higher than that absorbed during intravenous pyelography; the absorbed dose of a complete multiphasic CT examination is 3.7 for males and 4.6 for females (3.2 and 3.9 respectively after optimization) higher than that absorbed during intravenous pyelography. Such dosimetric data may be justified by diagnostic advantages in stone assessment, especially in males, and by the fact that multislice CT may unify different diagnostic tools such as intravenous pyelography, axial CT and angiography, thereby simplifying the entire diagnostic protocol. As far as exposure is concerned radiologists should follow the optimizing principle referred to each clinical query, bearing in mind that diagnostic accuracy is more important than the simple iconographic aspect.

Female↗
PubMed2004

The utility of computed tomography scans in predicting suboptimal cytoreductive surgery in women with advanced ovarian carcinoma.

BACKGROUND: Computed tomography (CT) scans of the abdomen and pelvis may predict which patients with ovarian carcinoma can undergo optimal cytoreduction at primary surgery. Previous studies have demonstrated that patients with ovarian carcinoma had optimal cytoreduction rates ranging from 50-60%. The authors sought to determine whether these findings applied to a surgical practice with a higher rate of optimal debulking. A predictive model using CT scanning and CA 125 values would allow the authors to determine which patients would be more appropriately treated with neoadjuvant chemotherapy. METHODS: Preoperative CT scans for patients with Stage III/IV ovarian carcinoma (according to the staging system of the International Federation of Gynecology and Obstetrics) who were treated between 1996 and 2001 were evaluated retrospectively by 2 radiologists for 17 criteria evaluating the extent of disease. Clinical data were extracted from medical records. Residual tumors measuring > or = 1 cm were considered suboptimal. Logistic regression was used to evaluate which criteria correlated with optimal cytoreduction. RESULTS: Eighty-seven patients were identified retrospectively who met entry criteria and had preoperative CT scans of sufficient diagnostic quality. Sixty-two patients (71%) received optimal cytoreductive surgery and 45 (52%) required aggressive surgical procedures. In a multivariate model, only diffuse peritoneal thickening (DPT) independently predicted suboptimal surgical resection (P = 0.016). However, a model using both DPT and ascites on most CT scans had a positive predictive value of 68% and a sensitivity of 52% for predicting suboptimal cytoreduction. CONCLUSIONS: The presence of DPT and large-volume ascites was associated with a very low rate of optimal cytoreduction (32%) in a surgical practice. These patients may be more appropriately treated with neoadjuvant chemotherapy followed by surgical cytoreduction.

Ascites↗
PubMedDate not supplied

Apparent racial disparity in the utilization of invasive testing for risk assessment of cardiac patients undergoing noncardiac surgery.

BACKGROUND: Studies on racial disparity in the use of cardiac diagnostic procedures are limited because they were conducted in the acute clinical setting without control for patient knowledge and emotional state or used models not controlling for racism. Using the setting (model) of elective evaluation of known, stable, cardiac patients undergoing noncardiac surgery, where the surgeon/anesthesiologist's personal interest precludes expression of potential racial bias, we assessed for racial differences in the utilization of diverse cardiac diagnostic procedures for risk assessment and optimization. METHODS: This is a secondary analysis of data from 314 consecutive patients [92 (29%) African-American, 222 (71%) Caucasian] with coronary artery disease (CAD), cardiomyopathy (ejection fraction <45%), or treatment-requiring arrhythmias, who underwent noncardiac surgery. RESULTS: The incidence of angina, prior myocardial infarction, and ischemic cardiomyopathy was higher in Caucasians (75%, 68%, and 164%, P<.0001, respectively), while nonischemic cardiomyopathy was more prevalent among African-Americans (84%, P<.0001). While, multivariately, African race predicted underuse of coronary angiography (odds ratio: 0.10, 95% confidence interval: 0.04-0.26, P<.0001), this predictor was eliminated when presence of CAD plus cardiomyopathy was factored in as a surrogate of severity. The use of noninvasive cardiac procedures and the 30-day mortality and morbidity did not differ by race. CONCLUSION: In a racism-proof model of preoperative evaluation of stable cardiac veterans, the racial disparity in the use of invasive procedures was related to epidemiologic differences. In addition, the parity in mortality and morbidity corroborates no underuse of diagnostic procedures among African-Americans.

Black People↗
PubMed1993

The palpable breast nodule. A cost-effectiveness analysis of alternate diagnostic approaches.

BACKGROUND: Traditionally, open biopsy has been considered the optimal procedure for the diagnosis of breast nodules. Fine-needle aspiration biopsy (FNAB) has been proposed as an alternate method for the diagnosis of many palpable breast lesions. METHODS: The authors compared the diagnostic utility of open biopsy and FNAB using decision tree and cost-effectiveness analyses. RESULTS: When compared with two-step excisional biopsy, FNAB achieved a savings of over $700 at the cost of 0.1% decrease in 10-year overall survival. CONCLUSIONS: These data indicate FNAB to be a reasonable alternative to open biopsy for the diagnosis of palpable breast lesions in many patients.

Adult↗
PubMed2002

Unusual variations of gastrointestinal smooth muscle abnormalities associated with chronic intestinal pseudo-obstruction.

The clinicopathological spectrum of gastrointestinal (GI) smooth-muscle abnormalities associated with chronic intestinal pseudo-obstruction (CIPO) includes numerous heterogeneous conditions that are often ill-defined and poorly understood. Primary GI smooth-muscle abnormalities include familial and sporadic forms. Secondary involvement of GI smooth-muscle may result from associated GI and systemic conditions, but is less frequent than in adults. This study documents the clinicopathological findings observed in 12 South African patients with unusual forms of visceral smooth-muscle abnormalities not conforming to the diagnostic criteria of known primary visceral myopathies at the Tygerberg and Red Cross Childrens' Hospitals over a 14-year period (July 1985 through January 1999). Congenital muscle defects occurred in 5 patients where layers of bowel-wall muscle were absent or attenuated. Idiopathic fibrosis and ultrastructural features of perinuclear and mitochondrial vacuolisation were noted in 2 patients. A 21-year-old female with long-standing pseudo-obstruction demonstrated diminished immunohistochemical expression of enteric alpha-smooth-muscle actin without associated muscular degeneration or fibrosis. A secondary complication of dermatomyositis (bowel perforation) occurred twice in 1 patient. In 3 further patients (1 each with anorectal malformation, long-segment Hirschsprung's disease, and intestinal neuronal dysplasia), muscle fibrosis appeared during progression of the pre-existing disease. Visceral myopathies are poorly understood conditions that may present with CIPO. Unusual variations occur that do not conform to the usual recognised histological patterns. Secondary involvement may also be more common than anticipated in children. The challenge to further understanding these uncommon conditions lies in timely diagnosis and identification of early, subtle signs. Optimal and extensive application of various diagnostic modalities, including the development of new diagnostic tools, is of considerable importance in identifying hitherto unexplained CIPO due to GI smooth-muscle abnormalities.

Adolescent↗
PubMed2001

[Optimizing image reconstruction timing for the RR interval in imaging coronary arteries with multi-slice computerized tomography].

PURPOSE: Multislice spiral CT is a newly developed technology that allows the non-invasive detection of coronary stenoses and plaques. The acquired raw data are reconstructed at a given time point in the RR interval of the heart cycle. Thus, determination of this time point is a key factor for picture quality and for reliable diagnostic results. This study was performed to investigate the optimal time point for reconstruction within the RR interval. MATERIALS AND METHODS: The coronary arteries of 13 patients were examined with CT. Raw data were reconstructed 250, 350, 450 and 550 ms before the following R wave (absolute reverse retrospective ECG gating) for each patient. Data were then analyzed with a volume rendering mode on a SIEMENS 3 D-Virtuoso workstation. A total of 91 segments (segments 1 and 2 of the RCA, segments 5, 6, 7 and proximal and distal parts of segment 11) were assessed and image quality was classified. RESULTS: Visualization of the left main coronary artery was of a good quality at all time points, segments 6 and 7 of the LAD as well as the proximal and distal parts of segment 11 of the RCX had the best quality at 450 ms absolute reverse retrospective ECG gating. The segments 1 and 2 of the RCA were of best quality 550% ms absolute reverse to the R peak. CONCLUSIONS: Classification of image quality of coronary artery CT scans after retrospectively ECG gated reconstruction is highly determined by the time point of reconstruction in the heart cycle. The optimization of this time point increases diagnostic accuracy and helps to avoid misinterpretation due to image artifacts.

Blood Flow Velocity↗
PubMed2006

Three-class ROC analysis--a decision theoretic approach under the ideal observer framework.

Receiver operating characteristic (ROC) analysis is well established in the evaluation of systems involving binary classification tasks. However, medical tests often require distinguishing among more than two diagnostic alternatives. The goal of this work was to develop an ROC analysis method for three-class classification tasks. Based on decision theory, we developed a method for three-class ROC analysis. In this method, the objects were classified by making the decision that provided the maximal utility relative to the other two. By making assumptions about the magnitudes of the relative utilities of incorrect decisions, we found a decision model that maximized the expected utility of the decisions when using log-likelihood ratios as decision variables. This decision model consists of a two-dimensional decision plane with log likelihood ratios as the axes and a decision structure that separates the plane into three regions. Moving the decision structure over the decision plane, which corresponds to moving the decision threshold in two-class ROC analysis, and computing the true class 1, 2, and 3 fractions defined a three-class ROC surface. We have shown that the resulting three-class ROC surface shares many features with the two-class ROC curve; i.e., using the log likelihood ratios as the decision variables results in maximal expected utility of the decisions, and the optimal operating point for a given diagnostic setting (set of relative utilities and disease prevalences) lies on the surface. The volume under the three-class surface (VUS) serves as a figure-of-merit to evaluate different data acquisition systems or image processing and reconstruction methods when the assumed utility constraints are relevant.

Algorithms↗