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Biomedical subjects

A W Lensing

Publications and source records attributed to A W Lensing.

70 records · Page 4Linked to original sources
PubMed1991

Deep vein thrombosis and fibrinolysis. Defective urokinase type plasminogen activator release.

In the present study 57 consecutive patients with a first episode of venographically proven deep vein thrombosis were investigated to evaluate the release of tissue-type plasminogen activator (t-PA) and of urokinase-type plasminogen activator (u-PA) in response to DDAVP stimulation as well as the resting plasminogen activator inhibitor (PAI) concentration, comparing this to the results obtained in 66 similar patients with a clinical suspicion of thrombosis but with a normal venogram. All assays were performed without knowledge of the patient's status. Four patients in the deep vein thrombosis-group (7%) had an absent u-PA antigen response upon DDAVP infusion, while a normal response was observed in all control subjects. Patients and controls showed similar increases in t-PA antigen level upon DDAVP. High resting PAI antigen levels were encountered in 5 patients in the deep vein thrombosis-group (9%) and in 6 subjects in the control group (9%). The results from this controlled study indicate that a defective release of u-PA may occur in patients with deep vein thrombosis and may have pathogenetic significance. Furthermore it is concluded that elevation of PAI levels cannot be considered as a specific risk factor for venous thrombosis.

Antigens↗
PubMed1991

A new computerized impedance plethysmograph: accuracy in the detection of proximal deep-vein thrombosis in symptomatic outpatients.

Because of the lack of specificity of the clinical diagnosis it is appropriate in patients with clinically suspected deep-vein thrombosis to apply an objective test before starting anticoagulant treatment. Impedance plethysmography is a highly accurate technique for the detection of proximal-vein thrombosis with a reported sensitivity and specificity of 93 and 97%, respectively. In all previous reported evaluations of impedance plethysmography an apparatus which was developed in 1971 was used. A new computerized impedance plethysmography, using a novel device to measure impedance, was blindly compared against venography in 443 consecutive outpatients with clinically suspected deep-vein thrombosis. In the first phase of the study the computerized impedance plethysmography test results of 242 symptomatic patients were used to develop a discriminant line. Subsequently, this discriminant line was validated in the second phase of the study in another 201 symptomatic patients. The combined sensitivity and specificity of these two phases for proximal-vein thrombosis was 91% [95% confidence interval (CI), 86 to 94%] and 94% and (95% CI, 90 to 96%), respectively, which compares favourably with impedance plethysmography. It is concluded that computerized impedance plethysmography is a simple, portable, non-invasive technique with a high accuracy for the detection of proximal vein thrombosis. However, before computerized impedance plethysmography can be used as the only test in the diagnosis of deep-vein thrombosis, the safety of withholding anticoagulant treatment to patients with repeated normal computerized test results should be assessed during long-term follow-up studies.

Adolescent↗
PubMed1991

Failure of computerized impedance plethysmography in the diagnostic management of patients with clinically suspected deep-vein thrombosis.

Before a new diagnostic modality can be introduced in clinical medicine, the validity of both a normal and abnormal test result have to be assessed prospectively in an appropriate patient group. We have evaluated the clinical validity of a new computerized impedance plethysmography (CIP) in the diagnostic management of 381 consecutive patients with clinically suspected venous thrombosis. In patients with serially normal CIP results, the diagnosis of venous thrombosis was refuted and, consequently, they were not treated with anticoagulant therapy and all were followed up for a period of 6 months to estimate the occurrence of symptomatic venous thromboembolism. The study was prematurely terminated by the safety monitoring committee because of an unacceptably high incidence of confirmed venous thromboembolism (10 patients, 3.2%; 95% confidence interval: 1.6% to 6%), including 4 episodes of fatal pulmonary embolism. In a subsequent explanatory study using ultrasonography in 29 other symptomatic patients who had at least 2 repeated normal CIP test results, the failure of CIP to detect proximal vein thrombosis was confirmed in 4 patients (14%). The reasons for this failure are probably related to the use of a modified device to measure impedance in the CIP apparatus, resulting in a lower ability to separate patients without venous thrombosis from those with the disease. We concluded that CIP is insensitive for the detection of proximal vein thrombosis and, therefore, not clinically useful in the diagnostic management of patients with suspected venous thrombosis.

Adolescent↗
PubMed1990

Diagnosis of deep-vein thrombosis using an objective Doppler method.

STUDY OBJECTIVE: To determine the diagnostic criteria (phase I) and to assess the accuracy (phase II) of an objective Doppler-Valsalva pressure method as compared with contrast venography for the diagnosis of acute deep-leg-vein thrombosis in symptomatic outpatients. DESIGN: A two-phase prospective study in consecutive patients. Doppler ultrasound strip-chart recordings and venograms were independently analyzed by experienced observers. SETTING: Referral-based medical clinics at university medical centers. PATIENTS: One hundred and ten (phase I) and one hundred and fifty-five (phase II) patients who had clinically suspected venous thrombosis and were referred by their general practitioners were included. METHODS AND MEASUREMENTS: A normal Doppler test result was defined as a cyclic spontaneous signal (S-signal), a continuous S-signal with a Valsalva pressure of less than 6.5 mm Hg, or an absent S-signal with flow after cessation of the Valsalva maneuver. A continuous S-signal with a Valsalva pressure of 6.5 mm Hg or more or an absent S-signal without flow after cessation of the Valsalva maneuver were defined as abnormal test results. The accuracy indices for proximal vein thrombosis in phase II (155 patients; prevalence, 31%) were sensitivity, 91% (95% CI, 79% to 98%), and specificity, 99% (CI, 97% to 100%). All 3 patients with isolated calf-vein thrombosis had normal Doppler test results. CONCLUSIONS: The objective Doppler method is an accurate, reproducible, and simple method for detection of venous thrombosis in symptomatic outpatients.

Abdomen↗
PubMed1990

Lower extremity venography with iohexol: results and complications.

The frequency of side effects of a nonionic contrast agent (iohexol) was studied in 463 consecutive patients who underwent venography for clinically suspected deep-vein thrombosis (DVT) and compared with the frequency of adverse reactions of another series in which patients received either the same contrast material or a high-osmolar ionic compound. Minor side effects, including local pain and discomfort, nausea and vomiting, dizziness, skin reactions, superficial phlebitis, and edema, occurred in 83 patients (17.9%; 95% confidence interval [CI], 15%-22%). The only serious adverse reaction (bronchospasm) was seen in two patients (0.4%; 95% CI, 0.1%-1.4%). Postvenographic thrombosis confirmed by means of repeat venography occurred in one of 41 consecutive patients with a previous normal venogram (incidence, 2%; 95% CI, 0%-13%). The frequency of side effects appears to be significantly less than when conventional high-osmolar contrast agents are used. Use of iohexol for venography is associated with minor side effects in approximately one-fifth of patients, and serious adverse reactions necessitating therapy are rare.

Adolescent↗
PubMed1989

Detection of deep-vein thrombosis by real-time B-mode ultrasonography.

In 220 consecutive outpatients with clinically suspected deep-vein thrombosis of the leg, we compared contrast venography with real-time B-mode ultrasonography, using the single criterion of vein compressibility with the ultrasound transducer probe. The common femoral and popliteal veins were evaluated for full compressibility (no thrombosis) and noncompressibility (thrombosis). Both veins were fully compressible in 142 of the 143 patients with normal venograms (specificity, 99 percent; 95 percent confidence interval, 97 to 100). All 66 patients with proximal-vein thrombosis had noncompressible femoral veins, popliteal veins, or both (sensitivity, 100 percent; 95 percent confidence interval, 95 to 100). For all patients (including 11 with calf-vein thrombi), sensitivity and specificity were 91 (95 percent confidence interval, 82 to 96) and 99 percent, respectively. The sensitivity for isolated calf-vein thrombosis was only 36 percent. The compression ultrasound test was repeated in a subset of 45 consecutive patients by a second examiner, unaware of the results of the first test, whose results agreed in all patients with those of the first examiner (kappa = 1). We conclude that ultrasonography with the single criterion of vein compressibility is a highly accurate, simple, objective, and reproducible noninvasive method for detecting proximal-vein thrombosis in outpatients with clinically suspected deep-venous thrombosis.

Femoral Vein↗
PubMedDate not supplied

New developments in noninvasive diagnosis of deep vein thrombosis of the lower limbs.

Since the clinical diagnosis of deep vein thrombosis (DVT) of the lower limbs is nonspecific, a confirmation by objective tests is mandatory. Recently, three new simple and reproducible methods of detecting DVT have been developed: computerized impedance plethysmography, standardized Doppler ultrasound, and compression ultrasonography. In three large prospective studies including consecutive outpatients with clinically suspected DVT, these tests were blindly evaluated versus phlebography, to determine diagnostic criteria and accuracy. The sensitivity for proximal DVT was 91% for computerized impedance plethysmography, 91% for standardized Doppler ultrasound and 100% for compression ultrasonography; sensitivity for all thrombi (including calf-vein thrombi) was 86, 85 and 91%, respectively; the specificity was 94% for computerized impedance plethysmography, and 99% for both standardized Doppler ultrasound and compression ultrasonography. The results of these studies demonstrate that all the three tests are highly specific and sensitive methods for the diagnosis of proximal DVT in symptomatic outpatients. However, isolated calf thrombi could not be detected adequately. Before these simple tests can be recommended as substitutes for phlebography, the safety of withholding anticoagulant therapy in patients with repeated normal tests should be assessed.

Evaluation Studies as Topic↗
PubMedDate not supplied

Noninvasive objective tests for the diagnosis of clinically suspected deep-vein thrombosis.

Deep-vein thrombosis of the lower extremity is a frequent disorder associated with morbidity and mortality due to pulmonary embolism and the postthrombotic syndrome. It was not until the introduction of contrast venography that the inaccuracy of the clinical diagnosis became apparent. Since then, management decisions have usually been based on objective diagnostic test. Venography is generally considered the reference method for the diagnosis of deep-vein thrombosis, but it is invasive and associated with serious side effects. Several noninvasive or less invasive objective diagnostic methods have been developed. These diagnostic methods are distinctly different in technology and consequently in their ability to demonstrate or refute deep-vein thrombosis. In this review, a critical analysis is provided on the accuracy of the current noninvasive diagnostic approaches to venous thrombosis in patients with a first episode of clinically suspected deep-vein thrombosis. Results of studies were considered only when their methodology fulfilled the essential criteria for evaluation of a diagnostic test.

Humans↗