Evaluation of competing tests for the diagnosis of pulmonary embolism and deep vein thrombosis, Part I.

Tests for pulmonary embolism (PE) and its most frequent source, deep vein thrombosis (DVT), include angiography, ventilation-perfusion nuclear medicine scans, venous sonography with Doppler, and contrast and radionuclide leg venography. Although selective angiography is the definitive procedure for the diagnosis of PE, the associated risk of death, although small, as well as the morbidity associated with injection of contrast agents, are high enough that alternative, less accurate, but safer diagnostic procedures are performed in an attempt to avoid the higher-risk procedure. Effective cost (EC) of each test represents the dollars spent per unit of diagnostic information and is defined as the ratio of the expected direct cost (EDC) of the test to its diagnostic performance (DU). EDC includes the base cost or charge of the test and the estimated cost of the morbidity and mortality that can be incurred in performing the test, while DU is determined from the test sensitivity and specificity. With the lowest EC as the selection criterion for the best test and representative costs, sensitivity, specificity, and morbidity and mortality rates, five different tests for PE or DVT were compared. Doppler sonography yielded the most diagnostic information per dollar spent, as its EC was the lowest, primarily because its base cost was low compared to that of the other tests. Radionuclide leg venography had the second lowest EC. Selection among the remaining three tests depended on the prevalence of PE and morbidity and mortality costs.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of competing diagnostic tests: sequences for the diagnosis of pulmonary embolism, Part II.

Tests for pulmonary embolism (PE) and its most frequent source, deep vein thrombosis, include angiography, ventilation-perfusion nuclear medicine scans, and contrast and radionuclide venography. Although selective angiography is the definitive procedure for diagnosis of PE, its risk of death, although small, as well as the morbidity associated with contrast injections, is high enough that alternative, less accurate but safer, diagnostic procedures are preferred. Part I of this report described the methodology for selection of the single test having the lowest effective cost based on the test cost, its risks, and diagnostic performance. Other than the pulmonary angiogram, however, no single test has a sufficiently high diagnostic performance to be clinically realistic: incorrect diagnoses can result in sudden death. Sequences of tests or algorithms can be used to lower the overall risk of the tests to patients while increasing correct decision making to reach a clinically acceptable level. These points are illustrated by comparing three commonly recommended algorithms for the diagnosis of PE. Additionally, the prevalence of PE affects the choice of the algorithm, and we found that no single algorithm is best for all values of prevalence. In summary, we found that the most cost-effective strategy was to select the particular algorithm having the lowest effective cost for the relevant prevalence value. Use of algorithms also decreased the overall risk of diagnostic test complications and the number of incorrect diagnoses.

The use of deep inspiration preceding the Valsalva maneuver and rapid expiration in color Doppler imaging of the lower extremity veins.

Deep inspiration preceding Valsalva maneuver and rapid expiration immediately following it (DIVE) enhance venous blood flow on color Doppler flow imaging (CDI). The effect of DIVE was assessed in 115 consecutive lower extremity examinations. Of these, 95 or 115 (83%) had negative CDI sonograms, and 20 of 115 (17%) had partially (six of 115) or completely (14 of 115) occluding deep vein thrombosis. DIVE enhanced venous blood flow in 68% of the negative cases, resulting in transient venous distention, and/or more complete color filling, and/or greater spectral flow velocities. The 14 cases with completely occluding thrombi showed no response to DIVE. Six cases with partially occluding thrombi showed moderate to mild response to DIVE, with improved color delineation of the residual patent lumen around the thrombus. The authors conclude that DIVE facilitates deep venous CDI, especially when compression cannot be used to augment venous flow.

Experimental design and fabrication of birdcage resonators for magnetic resonance imaging.

Although the birdcage resonator has been theoretically described for single- and multinuclear operation, this study provides the basic experimental guidelines needed for the fabrication and testing of such coils for various geometries and resonant frequencies from 10 to 95 MHz. The correlation of coil dimensions and resonant frequencies with individual inductance elements, L1 and L2, is also shown. Experimentally derived algorithms are presented for the determination of the capacitance needed for low-pass resonators based on measurements of the coil's "global" inductance. Ten low-pass birdcage coils with eight legs were evaluated and their four resonant frequencies were within 4% of theoretical predictions.

Quantitative MRI studies for assessment of multiple sclerosis.

Although magnetic resonance imaging (MRI) is a valuable aid in the initial diagnosis of multiple sclerosis (MS), quantitatively MRI has been disappointing in staging and evaluating therapy protocols by means of serial examinations. In this study, image processing algorithms were developed for the global analysis of MR images of the cerebrum. Limited three-dimensional segmentation was achieved through histogram analysis by these algorithms, which are essentially operator independent. The effects of coil response and tip angles, patient positioning, and interslice gap thicknesses were examined for 10 MS patients with repeated examinations for a total of 72 images. Effects of technique and instrumentation errors were approximately 6%, and agreement between two independent operators for measuring the total MR pixel sum from periventricular effusions and intense MS plaques was better than 97% with a standard deviation of 2.9%.

Detection of the fetus in the cul-de-sac by transabdominal and transvaginal ultrasound. A case report.

The most common reason for a fetus in the cul-de-sac is ectopic pregnancy, such as rupture of tubal pregnancy, ovarian pregnancy, and intraabdominal pregnancy (1-3). A case of the fetus in the cul-de-sac complicated by uterine perforation was imaged transabdominally and transvaginally on September 13, 1990.

The effect on grades of the timing and site of third-year internal medicine clerkships.

Two important factors affecting the performances of third-year medical students on their basic internal medicine clerkships were investigated: (1) the effect on their grades of when in the academic year they took the internal medicine clerkship, and (2) the effect on their grades of the site of the clerkship. During the academic years 1983-84, 1984-85, and 1985-86, the Department of Internal Medicine of the University of Illinois College of Medicine at Chicago conducted 12-week junior clerkships at six hospital sites. The study analyzed the 535 students' subjective grades, clerkship examination scores, final grades, and National Board of Medical Examiners Part I (NBME-I) scores. Although students' performances as characterized by subjective evaluations did not improve as the academic year progressed, mean scores on clerkship examinations improved steadily during the same period. The site of the clerkship, whether a community-affiliated hospital or a medical center hospital, affected neither subjective nor objective grades.

Optimizing radiologic costs in the DRG environment.

Previously developed consensus algorithms expressing a suggested radiologic workup for the diagnostic related groups (DRGs) specified by the prospective reimbursement policy have proven to be useful tools for investigating radiologic decision making and the resulting economic implications. The mathematical equations for determining diagnostic and therapeutic costs for two alternative algorithms for suspected acute cholecystitis are formulated. Illustrative examples and graphic displays are given regarding how such algorithms and equations are useful in finding answers to questions about the appropriate diagnostic workup, time, and cost. Exploration of the effect of different parameter values on the choice of the appropriate algorithm is illustrated.

Computed tomography versus magnetic resonance imaging of the brain. A collaborative interinstitutional study.

A retrospective study (1983-1984) of magnetic resonance imaging (MRI) and computed tomography (CT) examinations in 471 patients with known pathology in the brain and craniocervical junction was conducted in order to determine the relative efficacy of MRI versus CT. All MRI examinations involved slice thickness greater than 10 mm, and only single-slice single-echo or multislice single-echo imaging techniques were available. These studies were evaluated independently by two neuroradiologists from a panel of six for anatomic abnormalities, lesion contrast, and radiologist's impression. Results, which excluded microadenomas of the pituitary and approximately 9% of studies in which consensus was not achieved by the readers, were as follows: (1) 14% of the studies were positive on MRI but normal on CT; (2) in 55% of the studies, MRI was better than CT; (3) MRI was equal or better than CT in 95% of the studies; and (4) CT was better than MRI in 5% (21/421) of the examinations. There were no patients in this series where CT was positive but MRI missed the abnormality.

Diagnostic protocols for radiologic efficiency.

Starting January 1988, New York State started an all-payor prospective reimbursement for inpatient hospitalizations. Medicare had already adopted a prospective reimbursement system for its patients during the previous year. This article reviews our departmental efforts to prepare for the consequences of these new policies.

Unusual stress fracture of the scapula in a jogger.

A case of fracture of the right scapula in the superomedial portion with no history of direct trauma is presented. It is most likely due to jogging with weights in both hands. A brief review of scapular fractures is also reported.