Nonspecific binding in thyrotropin radioimmunoassay with double-antibody separation.
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Antibodies↗
Biomedical subjects
H R Maxon
Publications and source records attributed to H R Maxon.
Clinically important radiation-associated thyroid disease. A controlled study.
We evaluated 1,266 persons who had received external radiotherapy for benign diseases in childhood. The evaluation used detailed questionnaires completed by trained interviewers and neoplastic disease registry data. The control population included 958 age-, sex-, race-, and disease-matched persons who had not received radiotherapy and 9,865 family members of the two study groups. An excess number of clinically important thyroid neoplasms, both benign and malignant, was noted in the irradiated group.
Adolescent↗
Euthyroid, familial hyperthyroxinemia.
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Adult↗
A comparison of methods for assessing patient body burden following 131I therapy for thyroid cancer.
The effectiveness of three methods of assessing the patient body burden following 131I therapy was compared: (a) urine assay, (b) external exposure rate measurements, and (c) predictions based on a pretherapy diagnostic work-up. The urine assay method exhibited the greatest potential for error and personnel risk. The diagnostic work-up provided predictions of the body burden as a function of time, which may be applied to estimate the expected hospital stay. The direct external exposure rate survey showed the potential for being an accurate, reliable, and relatively safe method of monitoring the patient body burden.
Body Burden↗
Nonspecific binding as a source of error in thyrotropin radioimmunoassay with polyethylene glycol as separating agent.
We investigated the effects of nonspecific binding on thyrotropin values obtained by radioimmunoassay in which polyethylene glycol is used as precipitant. Differences in nonspecific binding among individual samples were significant (F-test, p less than 0.001, range 5.5 to 14.1%). Non-specific binding and total serum protein were directly correlated (r = 0.472, n = 59; p less than 0.001). Nonspecific binding increased with increasing concentrations of globulins but showed no relation to albumin concentration. If globulin concentration was less than 15 g/L, precipitation of the antigen--antibody complex by polyethylene glycol was incomplete. The mean value for thyrotropin in sera from 67 healthy subjects was 2.7 (SD 0.3) milli-international units per liter (milli-int. unit/L) without individual serum nonspecific binding correction, significantly (p less than 0.005) higher than that with nonspecific binding correction (1.6, SD 0.1, milli-int. unit/L). Evidently, inter-sample variations in nonspecific binding may cause significant errors under these conditions, which can be minimized by taking into account the individual nonspecific binding of each serum sample.
Evaluation Studies as Topic↗
Age-, sex-, and race-related differences in myoglobin concentrations in the serum of healthy persons.
A radioimmunoassay was used to study the relation of race, sex, and age to serum myoglobin concentrations in ostensibly healthy individuals: 75 white men, 76 white women, 75 black men, and 66 black women, ranging in age from 20 to 85 years. Mean serum myoglobin values were significantly higher in men than in women in both races (35 vs 31 microgram/L for whites and 44 vs 29 microgram/L for blacks). Black men had higher values than white men, but no corresponding difference was observed in the female population. Except for the group of black men, which consistently had the highest values for serum myoglobin, values were always higher for the older groups (greater than or equal to 50 years) than the younger, irrespective of race or sex. Serum myoglobin and age were significantly and directly correlated only among white men (r = 0.3408 p < 0.01, n = 75). If results were expressed as a myoglobin/creatinine ratio, the distinctions by race, sex, and age were partly eliminated. Reference intervals for serum myoglobin, expressed both ways, are given for different race, sex, and age groups.
Adult↗
Evaluation and comparison of two fully automated radioassay systems with distinctly different modes of analysis.
Two fully automated radioimmunoassay systems with batch and sequential modes of analysis were used to assay serum thyroxine, triiodothyronine, and digoxin. The results obtained were compared with those obtained by manual methods. The batch system uses antibody coated tubes while the sequential system uses immobilized antibody chambers for the separation of bound from free ligands. In accuracy, both systems compared favorable with the established manual methods, but the sequential system showed better precision than the batch system. There was a statistically significant carryover of thyroxine in the sequential system when there were at least six-fold differences in the concentrations of thyroxine in adjacent samples, but the carryover was not significant in the batch system. Compared with the batch system, the sequential system has a shorter throughtime for individual samples (time from aspiration of the sample to the printout of results) but a longer interval for final overall printout of assay results (lower throughput).
Analysis of Variance↗
Dose to the liver and spleen in pediatric patients undergoing technetium-99m sulfur colloid scans.
Quantitative conjugate view external counting techniques were applied to determine radiation dose to the liver and spleen in pediatric patients undergoing 99mTc-sulfur colloid (Tc-SC) liver scans. The effective half-life of 99mTc-SC was 5.8 +/- 0.23 hours and 5.2 +/- 0.68 hours in the liver and spleen, respectively. Dose per administered activity ranged from 0.34 to 0.63 rad/mCi (92 to 170 muGy/MBq) for the liver and 0.35 to 1.96 rad/mCi (95.0 to 530.0 muGy/MBq) for the spleen. The spleen to liver dose ratio ranged from 1.0 to 4.9. These values are compared with results extrapolated from published adult data to the pediatric population.
Adolescent↗
Nuclear power and health.
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Nuclear Reactors↗
Fallout at Three Mile Island.
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Air Pollution, Radioactive↗
A commercial digoxin radioassay modified for use as an emergency ("stat") procedure.
A recent "stat" procedure recommended by the manufacturer for use with a commercial digoxin radioassay involves doubling the amount of antibody used in the regular procedure, to compensate for the decrease in binding that results from use of a shorter (10 min) incubation. This has two obvious disadvantages: increased material cost and decreased sensitivity because of the increase in the binding capacity of the assay. In our modified procedure, we kept the binding capacity constant by decreasing the volume of the incubation mixture without increasing the amount of antibody. Total binding and the rate of binding on 10-min incubation are 50.4 and less than 1.3% per minute, respectively. Results by our modified stat procedure compare well with those by the manufacturer's suggested regular procedure in terms of sensitivity, accuracy, and precision, and are more sensitive and economical than those by the manufacturer's suggested stat procedure.
Digoxin↗
A statistical method for determining normal ranges from laboratory data including values below the minimum detectable value.
Determination of normal ranges from laboratory data containing undectable values is a frequently encountered problem in the radioimmunoassay of peptide hormones. In the past, such determinations usually have been based on the mid-point method or the one-end Winsorized method. A graphic method involving the use of probability paper has also been reported. We propose that the maximum-likelihood estimation is a more appropriate statistical method for the determination of normal range from this type of data (Type I censored data). With this method, the mean and standard deviation, and hence the tolerance limits, can be estimated. We used the maximum-likelihood estimation method to determine the normal range of serum thyrotropin values obtained from 93 healthy subjects, based on a log normal distribution. Although the serum thyrotropin content was undetectable in 14% of the subjects, a normal range could be calculated. Using tolerance limits for 95% coverage of the population with 90% confidence, we calculated the normal range of thyrotropin to be 0.51-5.75 milliunits/L, with a mean value of 1.71 milliunits/L, and predicted that 91.4% of undetectable serum thyrotropin values will fall within the normal range.
Humans↗
Dose to the metaphyseal growth complexes in children undergoing 99mTc-EHDP bone scans.
The spatial temporal distribution of radionuclides in children may differ greatly from that accepted for adults. Following injection of a bone-seeking agent (99mTc-EHDP), radioactivity in the metaphyseal growth complexes of the distal femur and proximal tibia was quantitated in a series of children 4 to 16 years of age, using a gamma camera/computer system. The dose to the growth plate was fount to range from 0.8 to 4.7 rads when adjusted to an administered activity of 200 muCi/kg, compared to approximately 0.6 rad to the adult skeleton for a corresponding study.
Adolescent↗
Clinical comparison of technetium-99m diphosphonate and pyrophosphate in bone scintigraphy: concise communication.
Thirty patients had bone scintigraphy with both Tc-99m pyrophosphate (Tc-PPi) and Tc-99m diphosphonate (Tc-HEDP). The images were given a composite rating for quality and the basis of three sets of criteria, and were also compared for the number of lesions detected by each agent. The two agents provided no difference in scan quality. Nevertheless, in ten of the 30 patients, at least two of the three readers detected with Tc-HEDP lesions that were not seen with Tc-PPi, and in two such cases all three readers considered the Tc-PPi scan normal. In another of these ten, two of three readers felt the Tc-PPi image was norm, whereas all three detected the lesion with Tc-HEDP. The reverse never occurred (P less than 0.01).
Bone Neoplasms↗
Emergency procedure for digoxin radioassay.
A rapid but precise radioassay for digoxin has been developed by optimizing the conditions for antigen-antibody interaction and for separation of bound and free fractions. This new procedure involves incubation of radioactively labeled antigen, antibody, and standard or sample at 3 degrees C for 10 min. Charcoal is then added, the mixture centrifuged for 5 min, and the radioactivity of the supernate counted. Results are available in less than 1 h after receipt of the specimens, making the procedure suitable for emergency determinations. Results correlate well with those by our routine procedure (Becton Dickinson) (r = 0.9739, y = 0.0356 + 0.9915x, n = 49). Analytical recovery of added pure digoxin exceeds 94%, both within and between assay CV's are less than 8%.
Antigen-Antibody Reactions↗
Hypercalcemia in thyrotoxicosis.
Hypercalcemia occurs in approximately one of every five patients with thyrotoxicosis, and one of seven patients with hypercalcemia and thyrotoxicosis will have hyperparathyroidism as the cause of the serum calcium elevation. While there are no clinical features which permit easy identification of patients with hyperparathyroidism and thyrotoxicosis, determination of serum parathyroid hormone levels may help. Parathyroid hormone levels may be normal or suppressed if hypercalcemia is due to hyperthyroidism alone, and an elevated parathyroid hormone level suggest coexisting hyperparathyroidism.
Adult↗
Ionizing irradiation and the induction of clinically significant disease in the human thyroid gland.
Because of increasing concern over continuing medical and potential nonmedical exposure of the thyroid to radiation, risk estimates have been developed for acute thyroiditis, hypothyroidism, and both benign and malignant thyroid nodules following exposure of the human thyroid to external and internal sources of ionizing radiation. These estimates are unique in that they are based entirely on data in human subjects are included corrections for the spontaneous occurrence of thyroid disease in human populations not subjected to radiation whenever possible.
Adolescent↗
Quantitative external counting techniques enabling improved diagnostic and therapeutic decisions in patients with well-differentiated thyroid cancer.
A quantitative technique is described which allows the physician to predict more accurately whether a recurrent or metastatic well-differentiated thyroid carcinoma is amenable to radioiodine-131 therapy or is better treated by other means. A calibrated uptake probe and scaler system is used to obtain conjugate view (i.e., diametrically opposed) counting rates for both the whole body and for any areas of abnormal uptake (lesion) at 24,48 annd 72 hours following the administration of 2 mCi 131l. Quantitative calculations accounting for patient attenuation, lesion size and geometrical factors then provide a determination of the lesion uptake as well as the effective half-life of 131l in the lesion. The radiation dose which would be delivered to the lesion by a given therapeutic amount of 131l may then be calculated to help determine the desirability of 131l treatment. The results of patient studies indicate the potential benefit of such quantitative evaluation.
Half-Life↗