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L R Witherspoon

Publications and source records attributed to L R Witherspoon.

34 records · Page 2Linked to original sources
PubMed1981

The triiodothyronine uptake test: an assessment of methods.

How well the free thyroxine index reflects thyroid functional status depends on the degree to which the triiodothyronine uptake test normalizes the effects of thyroxine binding protein concentrations on the total thyroxine concentration. We examined eight triiodothyronine uptake tests in which were used different secondary binders representative of those available in commercial kits. The relation between triiodothyronine uptake and thyroxine-binding globulin concentrations was established by use of sera from euthyroid individuals. We examined the effects of both high (greater than 20 mg/L) and low (less than 10 mg/L) thyroxine-binding globulin concentrations on triiodothyronine uptake. The precision of each assay, expressed as within- and between-run coefficient of variation, was calculated from multiple measurements on high, low, and midrange triiodothyronine uptake serum pools. The effects of variation in temperature and in exposure times were examined. The clinical most useful assays exhibited the ability to reflect a wide range of thyroxine-binding globulin concentrations and demonstrated little or no time or temperature effects.

Humans↗
PubMed1980

An evaluation of prepackaged columns for the separation of carcinoembryonic antigen from perchloric acid: concise communication.

Commerically available Sephadex buffer-exchange columns for the separation of carcinoembryonic antigen (CEA) from perchloric acid were evaluated. Elution patterns of individual columns were found to be variable, but separation of acid from CEA could be accomplished. Repeatability of replicate elutions and agreement with dialysis results were acceptable. Nevertheless, the method is excessively time-consuming and inefficient for processing large numbers of patient samples.

Buffers↗
PubMed1980

An assessment of methods for the estimation of free thyroxine.

Three commercial kit methods for the estimation of free thyroxine (FT4) (Clinical Assays, Corning Medical, Damon Diagnostics) were evaluated. The effects of changes in thyroxine-binding globulin (TBG) and FT4 concentrations in these systems were assessed. Measurements were made in serum samples from hyperthyroid, hypothyroid, and euthyroid patients with different TBG concentrations, and results were correlated with functional thyroid status. The Clinical Assays and Damon Diagnostics assays were found to be essentially independent of binding-protein concentration effects and responded appropriately to changes in FT4 concentration. The method of Corning Medical does not measure FT4 directly but yields an FT4 index calculated from a TBG-dependent T4 uptake and the total T4 concentration. This corning index yields falsely elevated results in patients with marked elevation in TBG concentration.

Evaluation Studies as Topic↗
PubMed1979

Assessment of serum myoglobin as a marker for acute myocardial infarction.

The reliability of serum myoglobin as a marker for acute myocardial infarction was evaluated in 157 consecutive coronary-care admissions. Admission myoglobin was elevated in 47 of 52 patients with acute infarction. Excluding those patients who presented later than 24 hr after symptom onset, only one patient with acute infarct had a normal admission myoglobin. In 22 of 105 patients with no infarct, myoglobin was elevated in association with angina, congestive heart failure, arrhythmias, and renal insufficiency. The detection of acute infarction by serum myoglobin measurement equals that of serial serum creatine phosphokinase isoenzymes (CPK-MB) by electrophoresis, but an elevated myoglobin is not specific for what is now considered clinically significant myocardial infarction.

Creatine Kinase↗
PubMed1979

Effects of contaminant radioactivity on results of 125I-radioligand assay.

Diagnostic radionuclide imaging procedures are often used in patients whose sera are later assayed by use of 125I-labeled radioligands; thus, it is important to identify those assays that potentially may be affected by contaminating radioactivity. Results obtained with assays in which specific separation methods (solid-phase primary antibody, second antibody) or small (10--25 micdo L) sample volumes are used are little affected by the presence of such contaminating radioactivity. Less-specific techniques (polyethylene glycol, charcoal, ion-exchange resin) segregate some of the contaminant activity into the bound fraction. The degree to which such activity is protein bound and the concentration of endogenous ligand then contribute to the resulting error in dose estimation. Samples for these assays should be screened for radioactivity before the assay is begun. Inclusion of nonspecific binding tubes for patients' samples when contamination is present permits the contaminating radioactivity to be evaluated and the patient's dose concentration to be more accurately estimated.

Chorionic Gonadotropin↗
PubMed1978

Spurious underestimation of results for digoxin radioimmunoassay with a commercial kit.

Estimates of digoxin in serum with a commercial redioimmunoassay kit (Schwarz/Mann) occasionally result in more counts in the patient's "bound" fraction than in the "bound" fraction for the zero standard. This phenomenon has been investigated in 26 serum samples obtained from patients who were ingesting known amounts of digoxin. The problem appears to relate to environmental differences in at least the zero standard and affects results when serum digoxin concentrations are less than 0.8 microgram/liter. Apparently dose estimates are more accurate with other methods or by calculating results after omitting the zero standard.

Digoxin↗
PubMed1976

Bone scan patterns of patients with diffuse metastatic carcinoma of the axial skeleton.

Bone scan findings (using 99mTc-stannous pyrophosphate) in five patients with diffuse metastatic carcinoma of the axial skeleton are reviewed. Although there were few visually recognizable asymmetries of tracer localization, the diffuse involvement was diagnosed through abnormally elevated counting rates in the axial skeleton, decreased visualization of the kidneys, and faint or absent visualization of the appendicular skeleton.

Adenocarcinoma↗
PubMed1975

Value of sequential postoperative brain scans in patients with anaplastic gliomas.

The authors analyze the postoperative course of 30 patients with anaplastic supratentorial gliomas to evaluate the usefulness of sequential brain scanning as an adjunct to clinical neurological examinations in the early detection of tumor recurrence. The correlation between sequential scanning and clinical evaluation was excellent; no examples of divergent resu;ts were seen. With the exception of scans made very early in the postoperative period or when postoperative scalp flap infections were present, initial postoperative scans were easily interpreted in terms of both the superficial (postcraniotomy) and parenchymal changes. The specific type of postoperative therapy (radiation therapy, chemotherapy, or both) could not be correlated with whether scan or examination ultimately changed first. However, analysis of original tumor location revealed that while sequential postoperative scanning offered no advantage over repetitive neurological examinations in the detection of recurrent tumor in the neurologically dominant left hemisphere, scan changes preceded examination changes in eight of 17 cases involving tumors of the neurologically nondominant right hemisphere.

Brain Neoplasms↗
PubMedDate not supplied

Characterization of malignant gliomas and cerebrovascular disease by cerebral dynamic studies.

A technique for analysis of dynamic radionuclide studies of the cerebral circulation is described. This technique permits objective classification of observed radionuclide distribution patterns. Variation in the time-to-peak activity, and in the maximum attained activity as determined by region-of-interest analysis of cerebral hemispheric activity, was defined for a normal population. Application of these normal values permits classification of observed hemispheric radionuclide distribution patterns in anaplastic gliomas and in occlusive cerebrovascular disease. Radionuclide activity in gliomas may be normal, decreased, or increased in the region of the tumor. In cerebrovascular occlusion, decreased activity, associated with a delay in time-to-peak activity, is frequently demonstrated in the affected hemisphere.

Brain Neoplasms↗