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M L Sampson

Publications and source records attributed to M L Sampson.

10 recordsLinked to original sources
PubMed2001

Triple lipid screening test: a homogeneous sequential assay for HDL-cholesterol, total cholesterol, and triglycerides.

BACKGROUND: The analysis of lipids in serum lipoprotein fractions is useful in assessing the risk for coronary artery disease, but it typically involves performing multiple tests. An automated single-tube assay, referred to as the triple lipid screening (TLS) test, can be used for measuring HDL-cholesterol (HDL-C), total cholesterol, and triglycerides (TGs) with no specimen pretreatment. METHODS: The first part of the assay is based on a homogeneous assay for HDL-C that uses either an anti-apolipoprotein B antibody (TLS-A test) or a polyanion (TLS-B test) that blocks the enzymatic measurement of cholesterol on the non-HDL fraction. After the addition of deoxycholate, which solubilizes the unreacted cholesterol from the non-HDL fraction, the remaining cholesterol in the sample is subsequently measured enzymatically. Using the same enzyme detection system as the cholesterol assay, TGs are measured in the last step, after the addition of the enzymes for the TG assay. RESULTS: The TLS assay (y) had acceptable analytic performance and compared favorably with standard tests (x) for each analyte: for HDL-C, TLS-A = 0.99x + 0.19 (R = 0.980); TLS-B = 1.00x - 0.15 (R = 0.974); for total cholesterol, TLS-A = 1.03x + 0.12 (R = 0.997); TLS-B = 1.07x - 0.30 (R = 0.965); and for TGs, TLS-A = 1.02x + 0.02 (R = 0.988); TLS-B = 1.04x - 0.28 (R = 0.980). CONCLUSIONS: The TLS test is a single-tube homogeneous assay for the analysis of all of the major serum lipoprotein fractions and can be used as a simple screening test for the detection of hyperlipidemia.

Autoanalysis↗
PubMed2000

Dual HDL/total cholesterol test: a single-tube, homogeneous assay for sequential measurement of HDL cholesterol and total cholesterol.

The quantitation of cholesterol in lipoprotein subfractions is valuable in estimating the risk for coronary artery disease, but requires multiple tests. We describe a relatively simple procedure, referred to as the dual HDL/total cholesterol (DHT) assay, which allows the sequential measurement of HDL cholesterol (HDL-C) and total cholesterol (total-C) in a single tube. HDL-C is first measured using a homogeneous assay that utilizes an anti-apolipoprotein B [apo(B)] antibody, which sterically blocks the enzymatic measurement of cholesterol on the non-HDL subfractions. Next, deoxycholate is added, which disrupts the antibody-apo(B) complex and allows the subsequent enzymatic measurement of the remaining cholesterol in the non-HDL subfractions. The DHT assay has an acceptable analytical performance and yields results similar to standard methods: for HDL-C, y(DHT) = 0.98x + 0.19, r=0.90; for total-C, y(DHT) = 1.11x - 0.09, r=0.99. In summary, the DHT assay is a homogeneous assay for both HDL-C and total-C, and provides a simple and cost-effective method for screening for hyperlipidaemia.

Antibodies↗
PubMed1999

Kinetic analysis of the rapid intraoperative parathyroid hormone assay in patients during operation for hyperparathyroidism.

BACKGROUND: Rapid intraoperative parathyroid hormone (RI-PTH) assay is used to guide adequacy of resection during operation for hyperparathyroidism. We compared the RI-PTH assay (15 minutes) with a standard PTH assay, determined whether the PTH half-life varied between patients, and constructed a kinetic analysis of the RI-PTH data. METHODS: Forty-five patients with hyperparathyroidism had blood sampled at baseline and at times after parathyroid resection. Intact PTH was determined using RI-PTH and a standard assay. Values were fitted to an exponential decay curve using the baseline and the follow-up time points. PTH half-life and the new postexcision baseline value were calculated from the decay curve. RESULTS: The RI-PTH assay and the standard PTH assay correlated well. Average PTH half-life was 1.68 +/- 0.94 minutes (0.42 to 3.81 minutes). A kinetic analysis yielded a formula for the generation of a PTH decay curve. Using a 50% reduction in RI-PTH at 5 minutes as the criterion for adequate resection, 2 patients were incorrectly classified as not being cured. These patients were correctly classified using the kinetic analysis. CONCLUSIONS: PTH half-life can vary substantially. A kinetic analysis may be more accurate in assessing adequacy of resection. This method allows the surgeon to interpret RI-PTH data independent of the timing of samples.

Adult↗
PubMed1999

Prevalence-value-accuracy plots: a new method for comparing diagnostic tests based on misclassification costs.

The clinical accuracy of diagnostic tests commonly is assessed by ROC analysis. ROC plots, however, do not directly incorporate the effect of prevalence or the value of the possible test outcomes on test performance, which are two important factors in the practical utility of a diagnostic test. We describe a new graphical method, referred to as a prevalence-value-accuracy (PVA) plot analysis, which includes, in addition to accuracy, the effect of prevalence and the cost of misclassifications (false positives and false negatives) in the comparison of diagnostic test performance. PVA plots are contour plots that display the minimum cost attributable to misclassifications (z-axis) at various optimum decision thresholds over a range of possible values for prevalence (x-axis) and the unit cost ratio (UCR; y-axis), which is an index of the cost of a false-positive vs a false-negative test result. Another index based on the cost of misclassifications can be derived from PVA plots for the quantitative comparison of test performance. Depending on the region of the PVA plot that is used to calculate the misclassification cost index, it can potentially lead to a different interpretation than the ROC area index on the relative value of different tests. A PVA-threshold plot, which is a variation of a PVA plot, is also described for readily identifying the optimum decision threshold at any given prevalence and UCR. In summary, the advantages of PVA plot analysis are the following: (a) it directly incorporates the effect of prevalence and misclassification costs in the analysis of test performance; (b) it yields a quantitative index based on the costs of misclassifications for comparing diagnostic tests; (c) it provides a way to restrict the comparison of diagnostic test performance to a clinically relevant range of prevalence and UCR; and (d) it can be used to directly identify an optimum decision threshold based on prevalence and misclassification costs.

Apolipoprotein A-I↗
PubMed1997

Fracture of the first cervical vertebra in a high school football player: a case report.

OBJECTIVE: To present the case of a high school football player with a burst fracture of the ring of C1 resulting from a "spearing" tackle. BACKGROUND: Cervical spine fractures are rare in collision sports, but their potentially grave consequences mean that they must be given special attention. Spearing was banned by the National Collegiate Athletic Association and the National Federation of High School Athletic Associations in 1976, and the number of cervical spine fractures in high school and college football players has fallen dramatically. However, cervical spine fractures do still occur, and they present a diagnostic challenge to sports medicine professionals. DIFFERENTIAL DIAGNOSIS: Cervical sprain. TREATMENT: Treatment consists of halo-vest immobilization. Surgical fusion may be necessary for unstable C1-C2 fractures, although initial halo-vest treatment is usually attempted. UNIQUENESS: A 17-year-old defensive back attempted to make a tackle with his head lowered. He was struck on the superolateral aspect of the helmet by the opposing running back. He remained in the game for another play, but then left the field under his own power, complaining of neck stiffness and headache. Physical examination revealed upper trapezius and occiput tenderness, bilateral cervical muscle spasm, and pain at all extremes of voluntary cervical movement. He was alert and oriented, with a normal neurologic examination. Treatment with ice was attempted but was discontinued due to increased pain and stiffness. Heat resulted in decreased pain and stiffness, but his symptoms persisted, and he was trans- ported to the emergency room. Plain radiographs were read as negative, but a CT scan demonstrated a burst fracture of Cl. He was treated with halo-vest immobilization for 8 weeks and a rigid cervical collar for 8 additional weeks. Physical therapy was then initiated, and normal cervical range of motion and strength were restored within 6 weeks. The athlete competed in track 6 months after the injury and continues to play recreational sports without difficulty. At clinical follow-up 8 months after injury, he had full, painless cervical range of motion and a normal neurologic examination. CONCLUSIONS: A potentially devastating cervical spine injury can present insidiously, without dramatic signs or symptoms. Therefore, sports medicine professionals must retain a high index of suspicion when evaluating athletes with cervical spine complaints.

Journal Article↗
PubMed1996

The differentiating agent phenylacetate increases prostate-specific antigen production by prostate cancer cells.

The prostatic-specific antigen (PSA) is the tumor marker most widely relied upon for the monitoring of patients with prostate cancer. Recently, declines in the serum concentrations of PSA have been advocated as a surrogate marker of tumor response in clinical trials of investigational antitumor agents. We examined the hypothesis that this postulate may not apply to the evaluation of drugs such as phenylacetate, a differentiating agent endowed with mechanisms of action different from those of classic cytotoxic chemotherapy. Using human prostatic carcinoma LNCaP cells as a model, we show that phenylacetate induces PSA production despite inhibition of tumor cell proliferation. Incubation of LNCaP cultures with cytostatic doses of phenylacetate (3-10 mM) resulted in a three- to fourfold increase in PSA secretion per cell. This appears to result from upregulation of PSA gene expression, as indicated by elevated PSA mRNA steady-state levels in treated cells. The increase in PSA production per cell was confirmed in rats bearing subcutaneous LNCaP tumor implants that were treated systemically with phenylacetate. Further comparative studies indicate that upregulation of PSA is common to various differentiation inducers, including all-trans-retinoic acid, 1,25-dihydroxyvitamin D3, and butyrate but is not induced by other antitumor agents of clinical interest such as suramin. We conclude that declines in PSA may be treatment specific and that the exclusive use of this criterion as a marker of disease response may mislead the proper evaluation of differentiating agents in prostate cancer patients.

Animals↗
PubMed1993

Effect of the fragile X anomaly on body proportions estimated by pedigree analysis.

The purpose of this study was to determine the effect of the fragile X syndrome on limb (upper limb length) and facial (ear length) measurements in relation to body height, which was considered as a covariate. The analysis was performed in 52 fragile X Caucasian families, including affected individuals as well as their normal relatives. The maximum likelihood analysis of complex pedigrees, under the assumption of multivariate normality, was used to select the best genetic model and to estimate model parameters. This method allowed us to test various assumptions concerning the effect of normal hereditary variation, as well as of genetic anomaly and other relevant factors, in the mean and variance of a quantitative trait, and to obtain the maximum likelihood parameters for these effects. The results demonstrated that, if the family factor is accounted for in a model, the fragile X condition affects growth of both upper limb length and ear length, disproportionately to body height.

Adult↗