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We evaluated the technical performance of the Ciba Corning ACS:180 automated immunoassay system for the following analytes: thyroid-stimulating hormone, free thyroxine, luteinizing hormone, follicle-stimulating hormone, prolactin, human chorionic gonadotropin, carcino-embryonic antigen, and prostate-specific antigen. The characteristics evaluated were: precision, carryover, linearity, lower limit of detection, analytical interferences, and comparison with other methods. Satisfactory results were obtained in the within-run and between-run precision studies. Neither sample nor reagent carryover was found for any assay. The range of linearity was acceptable. For some of the assays evaluated, the lower limit of detection was better than that claimed by the manufacturer. Correlation between ACS:180 methods and compared methods was adequate. We conclude that the ACS:180 offers good reliability, practicability, and performance capabilities.
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PMID:Evaluation of Ciba Corning ACS:180 automated immunoassay system. 751 May 90

Theoretically, optimal performance for an immunoassay system is achieved when both the interassay and within-run precisions are identical. Using the Ciba Corning ACS:180 automated immunoassay system, the authors made two simple changes to the operating procedures that allowed near-optimal analytic performance (as assessed with the interassay coefficient of variation determined by the protocol of the National Committee for Clinical Laboratory Standards) for four of six hormones: thyroid-stimulating hormone, luteinizing hormone, prolactin, and human chorionic gonadotropin. At low hormone concentrations, the 20% interassay coefficients of variation for the hormones assayed were as follows: free tetraiodothyronine, 1.74 pM; thyroid-stimulating hormone, .033 mIU/L; luteinizing hormone, .21 U/L; follicle-stimulating hormone, .69 U/L; prolactin, 5.03 mU/L; and human chorionic gonadotropin, 1.52 mU/L. The operational enhancements improved the analytic performance of the assay for all hormones assessed compared with the performance of previously used isotopic immunoassays.
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PMID:Simple procedures can markedly enhance automated immunoassay performance. 803 64

For a period of 12 months all samples submitted for serum prolactin (PRL) assay and with PRL > 700 mU/L were examined by gel filtration chromatography. In 17 (25%) of 69 samples we found macroprolactin. The Delfia and Immuno 1 immunoassay systems gave similar PRL results with samples containing macroprolactin whereas the ACS 180 system gave lower results. With the Delfia and Immuno 1 systems samples containing substantial quantities of macroprolactin showed low recovery of PRL after precipitation with polyethylene glycol 6000 (PEG 6000) and this technique can be used as a screening test for macroprolactinaemia. We conclude that macroprolactinaemia is a common phenomenon and, in assays which detect this species, is a common cause of hyperprolactinaemia. Macroprolactinaemia may contribute to the difficulty in establishing an upper limit of the reference range for serum PRL. In our experience, patients with macroprolactinaemia do not exhibit features of the hyperprolactinaemia syndrome and it is important to recognize macroprolactin as the cause of hyperprolactinaemia to avoid unnecessary investigation and treatment.
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PMID:Macroprolactinaemia: contribution to hyperprolactinaemia in a district general hospital and evaluation of a screening test based on precipitation with polyethylene glycol. 936 16

Macroprolactinemia, i.e. sustained hyperprolactinemia where the predominant circulating form of prolactin (PRL) is of large molecular weight, is a common phenomenon comprising up to one-fourth of all cases of hyperprolactinemia. We measured serum PRL levels by four different immunoassay systems (PROL-CTK, RIAgnost, Delfia, ACS 180) and by the Nb2 bioassay in patients with prolactinomas/idiopathic hyperprolactinemias in whom monomeric PRL was the major species of PRL (n=11, group 1) and in patients with macroprolactinemia (n=12, group 2). In group 1, the results obtained with the different immunoassays and with the Nb2 assay were highly correlated (r=0.945-0.982). On the other hand, big big-PRL (bb-PRL) was differently recognized by the immunoassays, since measured serum PRL values from each patient were highly variable in group 2. RIA-gnost Prolactin and Delfia Prolactin detected bb-PRL similarly and they were highly correlated with each other (r=0.937, p<0.0001). ACS 180 detected bb-PRL somewhat differently from the RIA-gnost and Delfia systems, but likewise most of the patients of group 2 had PRL values above normal. PROL-CTK was the method less influenced by the presence of bb-PRL since most of the subjects with macroprolactinemia had PRL levels either within the normal range or only marginally elevated. From the immunoassays tested, PROL-CTK was the system which was less correlated with the Nb2 bioassay in group 2 (r=0.252; NS). Our experience is that macroprolactinemia is an asymptomatic condition in most of the cases. Therefore, we suggest that the routine measurement of PRL should be done with methods that are only minimally affected by the presence of macroprolactin. Such an approach would obviate the use of extensive, frequently expensive and ultimately useless diagnostic tests that are needed to determine the cause of the hyperprolactinemia.
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PMID:Hyperprolactinemia due to big big prolactin is differently detected by commercially available immunoassays. 1021 88

Hydrocortisone, progesterone, testosterone, triiodothyronine, thyroxine, chorionic gonadotropin, prolactin, alpha-fetoprotein, luteinizing, follicle-stimulating, and thyrotropic hormones were measured in human sera and in Lyphochek Immunoassay Plus Control reference sera (Bio-Rad Laboratories, USA) using 4 commercial kits (Alkor Bio Inc. and Roche, automated analyzer Roche Cobas Core; DPC, automated analyzer Immulite; Bayer, automated analyzer ACS:180). Coordination and correlation between these kits was observed, the coordination decreasing in the series Alkor Bio/Bayer, Alkor Bio/Roche, and Alkor Bio/DPC.
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PMID:[Comparative analysis of serum analyte level measurements by commercial diagnostic kits from four manufacturers (Alkor-Bio, Roche, Diagnostic Products Corporation-DCP, and Bayer Corporation)]. 1241 3

A high molecular mass form of prolactin (PRL), macroprolactin, accumulates in the sera of some subjects. Although macroprolactin exhibits limited bioactivity in vivo, it retains immunoreactivity. We examined the frequency of macroprolactinemia in clinical practice and the ability of immunoassay systems to distinguish between macroprolactin and monomeric PRL. Of 300 hyperprolactinemic sera identified, 71 normalized following treatment of sera with polyethylene glycol, indicating that 24% of hyperprolactinemia could be accounted for by macroprolactin. Ten of these macroprolactinemic sera were circulated to 18 clinical laboratories. Two sets of PRL measurements of the 10 untreated sera were obtained from each of the nine most commonly used immunoassay systems. Across the nine assay systems, differences in the PRL estimates ranged from 2.3- to 7.8-fold. Elecsys users reported the highest PRL levels. Somewhat lower values were reported for DELFIA systems followed by Immuno-1, AxSYM, and Architect assays. The Immulite 2000 assay generated PRL levels equivalent to approximately 50% of those reported by the high-reading methods. The lowest PRL levels were reported by Access, ACS:180, and Centaur systems. To avoid confusion caused by the frequent presence of macroprolactin accounting for hyperprolactinemia, secondary screening for the presence of macroprolactin is recommended.
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PMID:Gross variability in the detection of prolactin in sera containing big big prolactin (macroprolactin) by commercial immunoassays. 1246 26

We have recently reported G-protein coupled receptor (GPCR) model structures for the active and inactive states of the human dopamine D2 receptor (D2R) using adrenergic crystal structures as templates. Since the therapeutic concentrations of dopamine agonists that suppress the release of prolactin are the same as those that act at the high-affinity state of the D2 receptor (D2High), D2High in the anterior pituitary gland is considered to be the functional state of the receptor. In addition, the therapeutic concentrations of anti-Parkinson drugs are also related to the dissociation constants in the D2High form of the receptor. The discrimination between the high- and low-affinity (D2Low) components of the D2R is not obvious and requires advanced computer-assisted structural biology investigations. Therefore, in this work, the derived D2High and D2Low receptor models (GPCR monomer and dimer three-dimensional structures) are used as drug-binding targets to investigate binding interactions of dopamine and apomorphine. The study reveals a match between the experimental dissociation constants of dopamine and apomorphine at their high- and low-affinity sites of the D2 receptor in monomer and dimer and their calculated dissociation constants. The allosteric receptor-receptor interaction for dopamine D2R dimer is associated with the accessibility of adjacent residues of transmembrane region 4. The measured negative cooperativity between agonist ligand at dopamine D2 receptor is also correctly predicted using the D2R homodimerization model.
ACS Chem Neurosci 2016 Feb 17
PMID:Binding Interactions of Dopamine and Apomorphine in D2High and D2Low States of Human Dopamine D2 Receptor Using Computational and Experimental Techniques. 2664 29