Indeterminate Scans Research Articles

Suspected pulmonary embolism and lung scan interpretation

To determine whether a Bayesian method of lung scan (LS) reporting could influence the management of patients with suspected pulmonary embolism (PE). 1) A descriptive study of the diagnostic process for suspected PE using the new reporting method; 2) a non-experimental evaluation of the reporting method comparing prospective patients and historical controls; and 3) a survey of physicians' reactions to the reporting innovation. University of Virginia Hospital. Of 148 consecutive patients enrolled at the time of LS, 129 were completely evaluated; 75 patients scanned the previous year served as controls. The LS results of patients with suspected PE were reported as posttest probabilities of PE calculated from physician-provided pretest probabilities and the likelihood ratios for PE of LS interpretations. Despite the Bayesian intervention, the confirmation or exclusion of PE was often based on inconclusive evidence. PE was considered by the clinician to be ruled out in 98% of patients with posttest probabilities less than 25% and ruled in for 95% of patients with posttest probabilities greater than 75%. Prospective patients and historical controls were similar in terms of tests ordered after the LS (e.g., pulmonary angiography). Patients with intermediate or indeterminate lung scan results had the highest proportion of subsequent testing. Most physicians (80%) found the reporting innovation to be helpful, either because it confirmed clinical judgement (94 cases) or because it led to additional testing (7 cases). Despite the probabilistic guidance provided by the study, the diagnosis of PE was often neither clearly established nor excluded. While physicians appreciated the innovation and were not confused by the terminology, their clinical decision making was not clearly enhanced.

Pleuroperitoneal Communication Associated with Malignant Ascites

A patient with metastatic gastric carcinoma and malignant ascites developed sudden-onset dyspnea secondary to a new large left pleural effusion. A radionuclide lung scan performed for suspected pulmonary embolism was indeterminate. Scintigraphy performed following intraperitoneal administration of Tc-99m sulfur colloid subsequently demonstrated rapid accumulation of activity in the left pleural space, indicating the presence of a pleuroperitoneal communication. In a patient with known or suspected ascites, a new pleural effusion, and an indeterminate lung scan, peritoneal scintigraphy may identify the origin of the effusion and obviate the need for further invasive evaluation for possible pulmonary embolism.

Clinical presentation and investigation of patients proceeding to isotope lung scanning for suspected pulmonary embolism

The presenting features of 250 consecutive patients who underwent a ventilation/perfusion lung scan for suspected pulmonary embolus (PE) were analysed. Ninety-six patients had lung scans highly suggestive of PE, with one or more unmatched segmental perfusion defects (scan positive), 86 had low probability scans (scan negative) and 68 an indeterminate scan. Scan positive patients were more likely to have a PaO2 of less than 10.7 kPa, an elevated P(A-a)O2 and an abnormal chest X-ray compared with scan negative patients but these measurements were of poor specificity. Furthermore, scan-positive patients had a higher incidence of lung disease. Localized chest wall tenderness was more common in scan-positive patients, occurring in 9% of patients, but there were no other significant differences in individual symptoms, signs or electrocardiographic findings between scan-positive and scan-negative patients. The diagnosis of PE should not be made on clinical grounds alone and all patients suspected of having a PE should at least undergo isotope lung scanning.

Laboratory diagnosis of pulmonary embolism: value of increased levels of plasma D-dimer and thrombin—antithrombin III complexes

Plasma D-dimer (DD) and thrombin—antithrombin III complex (TAT) were measured with ELISAs in 99 patients investigated by 102 ventilation—perfusion lung scintigraphy because of suspected pulmonary embolism. High-probability lung scan was associated with increased DD (more than 500 ng/ml) and TAT (more than 4.1 ng/ml) levels (sensitivity of 100 and 70%, respectively). The corresponding figures of specificity were 81 and 42%. In the 56 patients with low-probability or indeterminate probability scans, 31 (55%) had DD concentrations of less than 500 ng/ml. These preliminary data suggest that a plasma DD concentration of less than 500 ng/ml might rule out the diagnosis of pulmonary embolism in suspected patients with an inconclusive lung scanning.

Diagnosis of pulmonary embolism

The clinical diagnosis of pulmonary embolism is highly nonspecific because none of the symptoms or signs of pulmonary embolism is unique and all may be caused by other cardiorespiratory disorders. Thus, objective testing is mandatory to either confirm or exclude a diagnosis of pulmonary embolism. Based on current available information, a diagnostic approach for the management of clinically suspected pulmonary embolism is proposed. After a history and physical examination, electrocardiogram and chest X-ray film, all patients should undergo perfusion lung scanning. The finding of a normal perfusion lung scan rules out clinically significant pulmonary embolism, and anticoagulant therapy is withheld. The management of patients with an abnormal perfusion lung scan is more complex. If this scan demonstrates one or more segmental (or greater) perfusion defects, ventilation lung scanning should be performed because the probability of pulmonary embolism is markedly increased if a mismatch is found, with a high probability scan (positive predictive value 86%) providing an end point for commencing anticoagulant therapy in the majority of patients. In an abnormal ventilation-perfusion study, the presence of a ventilation-perfusion match does not rule out the possibility of pulmonary embolism, and further objective testing is required in these patients with nonhigh probability scans. Similarly, in patients with small perfusion defects (one or more subsegmental defects) or indeterminate lung scan findings (in which the perfusion scan defects correspond to a defect on a chest X-ray film), the predictive values obtained from these ventilation-perfusion scan patterns are not sufficiently high or low to confirm or exclude the presence of pulmonary embolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of computed axial tomography of the chest in staging patients with nonmetastatic gestational trophoblastic disease.

Thirty-nine women with nonmetastatic gestational trophoblastic disease as determined by conventional staging studies were prospectively evaluated with computed axial tomography (CAT) of the lungs. Sixteen patients (41%) had pulmonary micrometastases detected by CAT, which were not detected by routine chest x-ray. Eight patients (20.5%) had indeterminate scans, and only 15 patients (38%) had negative scans. Eight of 16 patients (50%) with pulmonary micrometastases failed initial therapy with methotrexate-folinic acid rescue while one of eight (12.5%) patients in the indeterminate group and one of 15 (6.7%) patients in the true nonmetastatic group failed initial therapy (P less than .006). All patients who failed methotrexate-folinic acid rescue ultimately achieved prolonged remission with actinomycin D. Time to remission was significantly decreased in patients without evidence of pulmonary micrometastases (P = .03), but the total number of courses of chemotherapy was not significantly different (P = .06). No life-threatening toxicity occurred. Pulmonary micrometastases detected by CAT but not chest x-ray are predictive of an increased risk of methotrexate-folinic acid therapy failure. Computed axial tomography of the lungs identifies a group of patients at high risk for failure of methotrexate-folinic acid rescue, and, therefore, may be indicated for routine staging of patients with otherwise nonmetastatic gestational trophoblastic disease.

Can Ventilation-Perfusion Scans Accurately Diagnose Acute Pulmonary Embolism?

To examine the accuracy of ventilation-perfusion (V/Q) scanning, we retrospectively reviewed pulmonary angiograms and V/Q scans from 150 patients clinically suspected of having pulmonary embolism. Pulmonary emboli were documented by angiography in 56 patients (37%). In seven patients V/Q scans were interpreted as being normal and these seven patients were angiographically negative for emboli. The remainder of the scans were classified as showing a low, moderate, or high probability of emboli, or as indeterminate scans. Among these four abnormal classifications, pulmonary angiography demonstrated emboli in 13.6%, 62.5%, 85.7%, and 18.4% of these patients, respectively. An analysis of these data demonstrates that an unacceptably high error rate would result if V/Q scans alone were relied upon to establish the presence or absence of pulmonary emboli. In view of the high mortality that results when pulmonary emboli are untreated and the relatively low mortality and morbidity of pulmonary angiography, angiography remains an essential diagnostic procedure in patients suspected of having pulmonary embolism.

Acute acalculous cholecystitis: sensitivity in detection using technetium-99m iminodiacetic acid cholescintigraphy.

Forty-one proved cases of acute acalculous cholecystitis imaged with technetium-99m iminodiacetic acid (IDA) cholescintigraphy were retrospectively analyzed. After the exclusion of one indeterminate scan (showing poor initial hepatic uptake and excretion), the study yielded a 92.5% (37 of 40) sensitivity for the detection of cystic or common bile duct obstruction. Each of the three patients with false-negative scintigrams had other abnormal scintigraphic findings suggestive of biliary tract disease. Of the 20 patients (48.8%) with focal or diffuse gangrenous cholecystitis or perforation, seven (35%) exhibited either free peritoneal spill or increased pericholecystic activity to indicate the presence of advanced disease.

Low sensitivity of plasma DNA in screening for pulmonary embolism.

Detection of plasma deoxyribonucleic acid (DNA) by counterimmunoelectrophoresis (CIE) has been proposed as a rapid, inexpensive screening test for the diagnosis of pulmonary embolism (PE). To test the sensitivity of plasma DNA detection for the diagnosis of PE, we obtained blood samples from 89 patients when they underwent lung scanning for suspected PE. Plasma was analyzed qualitatively for DNA by CIE, using antiserum that could detect as little as 0.2 micrograms DNA/ml. Among 16 patients with PE diagnosed by high probability lung scan, pulmonary angiography, or at autopsy, plasma DNA was detected in 3 patients--a sensitivity of 19%. Of 6 patients with indeterminate lung scans and a possible diagnosis of PE, 1 had detectable plasma DNA. None of the 67 patients without a diagnosis of PE had detectable plasma DNA, so the specificity was 100%. Thus, although detection of plasma DNA by CIE has many desirable features of a screening test, further studies are needed before this test can be recommended in routine screening for PE.

Hepatobiliary Scan and Acute Cholecystitis: Bayesian Analysis of Data-Reply

In Reply.— Predictive values (posttest probabilities) are helpful in conveying the importance of a given test result to the referring physician. However, Bayesian analysis requires that a test result be normal (negative) or abnormal (positive). Such an analysis was not emphasized in our article because of the presence of a third possibility, the indeterminate scan pattern. To present our results, the two indeterminate scans in the AC group were considered not to be true-positive studies, but they are definitely not false-negative studies as characterized by Dr Barenholtz. The referring physician is told that the patient has an abnormal study that does not discriminate between AC and other disease entities. Thus, the predictive value of a normal (negative) study in this series is 100% as stated in our article and not 98%. Bayesian analysis is also useful in defining the population best and least suited for a diagnostic test of

The Role of Gallium-67 Scanning in the Clinical Staging and Preoperative Evaluation of Patients with Carcinoma of the Lung

Gallium-67 scanning was evaluated in 100 patients with proved carcinoma of the lung. It was valuable in separating primary from secondary lung tumors, determining the extent of contralateral hilar or mediastinal lymph node involvement, and detecting distant organ metastases. In addition to multiplane whole-body Ga-67 tomographic scanning, colloid liver scans, bone scans, and computerized axial tomography scans of the brain were obtained to determine the presence of distant metastasis. The gallium scan detected 11 of 12 occult metastases and identified 7 of 7 liver, 9 of 14 brain, 4 of 4 soft tissues, 1 of 4 contralateral lung, and 9 of 11 bone metastases. The whole-body gallium scan accurately detected or excluded extrathoracic metastatic disease in 11 of 12 patients examined postmortem within three months of a gallium scan. An approach is recommended using gallium scanning along with chest roentgenograms for clinical staging and preoperative evaluation of patients with carcinoma of the lung. Specific organ scans should be reserved for the occasional symptomatic patient with a negative gallium scan or for clarification of an indeterminate gallium scan.