Monoclonal Immunoradiometric Assay Research Articles

Neuroendocrine differentiation in stage D2 prostate cancers

Chromogranin A (CgA) and neuro-specific enolase (NSE) are gaining acceptance as markers of several types of neuroendocrine tumors and the concentration of CgA and NSE have been reported to be elevated in relation to neuroendocrine differentiation of prostate cancer. The aim of the present study was to examine the correlation between the immunohistochemical (IHC) findings and serum value for CgA and NSE in untreated stage D(2) prostate cancer patients. Immunohistochemistry was carried out using antibodies against CgA and NSE in 58 patients and, pretreatment serum CgA and NSE levels were measured by monoclonal immunoradiometric assay in 18 patients with stage D(2) prostate cancer treated by androgen ablation. We examined the relationship of the pretreatment serum level to IHC findings for CgA and NSE in prostate cancer patients to clinicopathological parameters, and prognosis. Also, we evaluated the correlation of IHC findings to serum levels for CgA and NSE. There was a statistically significant correlation between CgA positivity and serum CgA level (P = 0.0421). However, there was no statistically significant correlation between NSE positivity and serum NSE level (P > 0.05). We divided stage D(2) patients into three groups according to IHC positivity of CgA and NSE. The cause-specific survival was significantly poorer in patients with strongly positive (++) patients for independent CgA and combined CgA with NSE (P = 0.0379). Multivariate analysis of cause-specific survivals in patients with stage D(2) prostate cancer demonstrated that strong IHC stain was considered as independent variable associated with greater risk of death (P = 0.0142). Neuroendocrine differentiation in stage D(2) prostate cancer has attracted considerable attention as a potentially findings prognosis. Thus, CgA had a stronger relationship between serum levels and IHC positivity in contrast to NSE, suggesting clinical usefulness as a tumor marker in predicting the extent of neuroendocrine differentiation in prostate cancer.

Effect of human chorionic gonadotropin on luteal luteinizing hormone concentrations in natural cycles

Effect of human chorionic gonadotropin on luteal luteinizing hormone concentrations in natural cycles

Chromogranin a concentration as a serum marker to predict prognosis after endocrine therapy for prostate cancer.

Chromogranin A is gaining acceptance as a serum marker of neuroendocrine tumors and the concentration is thought to be elevated in relation to neuroendocrine differentiation of prostate cancer. We examined the significance of the chromogranin A level as a serum marker for prostate cancer. Serum chromogranin A values were determined by monoclonal immunoradiometric assay in 108 patients with prostate cancer before treatment and in 66 with benign prostatic hyperplasia. In those with prostate cancer clinicopathological parameters, the response to endocrine therapy and the prognosis were evaluated in relation to serum chromogranin A. Mean serum chromogranin A plus or minus standard deviation in prostate cancer and benign prostatic hyperplasia cases was 59.4 +/- 52.5 and 59.3 +/- 44.3 ng./ml., respectively (not significant). Poorly differentiated adenocarcinoma was associated with higher chromogranin A than well differentiated disease (p = 0.044). Of the stage D cases with a median prostate specific antigen (PSA) of 172.1 ng./ml. or less those with higher chromogranin A had a poorer prognosis than those with lower chromogranin A. In contrast, in stage D cases with a PSA of greater than 172.1 ng./ml. there was no difference in the prognosis between the higher and lower chromogranin A groups. Serum chromogranin A tends to be elevated in patients with high grade prostate cancer. When combined with PSA, this marker may effectively predict a poor prognosis after endocrine therapy.

CHROMOGRANIN A CONCENTRATION AS A SERUM MARKER TO PREDICT PROGNOSIS AFTER ENDOCRINE THERAPY FOR PROSTATE CANCER

Chromogranin A is gaining acceptance as a serum marker of neuroendocrine tumors and the concentration is thought to be elevated in relation to neuroendocrine differentiation of prostate cancer. We examined the significance of the chromogranin A level as a serum marker for prostate cancer. Serum chromogranin A values were determined by monoclonal immunoradiometric assay in 108 patients with prostate cancer before treatment and in 66 with benign prostatic hyperplasia. In those with prostate cancer clinicopathological parameters, the response to endocrine therapy and the prognosis were evaluated in relation to serum chromogranin A. Mean serum chromogranin A plus or minus standard deviation in prostate cancer and benign prostatic hyperplasia cases was 59.4 +/- 52.5 and 59.3 +/- 44.3 ng./ml., respectively (not significant). Poorly differentiated adenocarcinoma was associated with higher chromogranin A than well differentiated disease (p = 0.044). Of the stage D cases with a median prostate specific antigen (PSA) of 172.1 ng./ml. or less those with higher chromogranin A had a poorer prognosis than those with lower chromogranin A. In contrast, in stage D cases with a PSA of greater than 172.1 ng./ml. there was no difference in the prognosis between the higher and lower chromogranin A groups. Serum chromogranin A tends to be elevated in patients with high grade prostate cancer. When combined with PSA, this marker may effectively predict a poor prognosis after endocrine therapy.

The value of serum tissue polypeptide specific antigen in the diagnosis of hepatocellular carcinoma

Tissue polypeptide specific antigen (TPS) recently was introduced as an indicator of cell proliferation in various tumors. The authors investigated the value of serum TPS as a complement to alpha-fetoprotein (AFP) in the detection of hepatocellular carcinoma (HCC) in Chinese patients. Serum TPS and AFP levels were measured by monoclonal immunoradiometric assay in 85 subjects (52 males and 33 females): 26 with HCC, 30 with chronic hepatitis (CH), and 29 healthy controls. Patients with HCC had significantly higher TPS levels compared with healthy controls (P < 0.05). However, the difference between the HCC and CH groups was not significant (P = 0.18). The sensitivity and specificity of TPS were 73.1% and 71.2%, respectively, with a cutoff value of 164 U/L for HCC diagnosis. TPS had lower discriminatory power compared with AFP (72.1% vs. 79.2%). In addition, TPS had a much lower specificity compared with AFP (89.1%). Combining the cutoff values for serum TPS and AFP levels in a pessimistic prognostic rule increased the sensitivity by 11.6% from 69.2% using serum AFP levels alone, but reduced the diagnostic power by 3.7% to 75.5% due to an 18.9% decrease in specificity to 70.2%. Using TPS alone offers no advantage over AFP for the diagnosis of HCC in Chinese patients. In conjunction with AFP, TPS reduced the false-negative rate. However, the clinical utility of the combined prognostic rule is limited due to the poor discriminatory power of TPS for HCC and CH. Therefore, the use of serum TPS levels in the detection of HCC is not recommended.

Influence of Local Tumour Stage and Grade on Reliability of Serum Prostate-Specific Antigen in Predicting Skeletal Metastases in Patients with Adenocarcinoma of the Prostate

Objective: To determine whether serum prostate-specific antigen (PSA) can be reliably used to predict the absence or presence of skeletal metastases on the bone scan in patients with adenocarcinoma of the prostate. Methods: We studied 450 consecutive men presenting with adenocarcinoma of the prostate between 1991 and 1995. Serum PSA was measured by the Hybritech Tandem-R monoclonal immunoradiometric assay and bone scanning was performed with 99m-technetium-labelled methylene diphosphonate. In total, 46 patients were excluded for one or more of the following reasons: serum PSA not available; radionuclide bone scan inconclusive; histology of the prostate other than adenocarcinoma; hormonal or other therapy given prior to obtaining the serum PSA and/or bone scan. Results: Of the 404 patients incluced, 43% had poorly differentiated (grade 3), 74% had locally advanced (stages T3–4) tumours and 50% had skeletal metastases. The mean and median serum PSA were 348 and 52 ng/ml, respectively, and 77% of the patients had a serum PSA >20 ng/ml. The negative predictive value (for the absence of metastases on bone scan) of a serum PSA <20 ng/ml was 87% for the whole group of patients, 92, 94 and 70% for grade 1, 2 and 3 tumours, and 95, 83 and 50% for stage T1–2, T3 and T4 tumours, respectively. The positive predictive value (for the presence of metastases on bone scan) of a serum PSA >100 ng/ml was 80% for the whole group of patients. Conclusions: In patients presenting with adenocarcinoma of the prostate, serum PSA alone is not sufficiently reliable to predict the absence or presence of metastases on the radionuclide bone scan. In patients with grade 3 and clinical stage T3–4 tumours, a bone scan should be obtained for accurate staging, regardless of the serum PSA value.

Correlation Between CSF and Serum S-100 Protein after Cerebral Ischemia in Pigs on Cardiopulmonary Bypass

Introduction: One potential marker of central nervous system damage during cardiac surgery is the astroglial protein S-100, which has been shown to increase with the duration of cardiopulmonary bypass (CPB) [1]. However, recovery of the S-100 protein in blood has not been directly correlated with functional or histopathological outcomes after CPB. Part of the diagnostic problem may be related to whether concentration of this protein marker in the serum correlates with cerebrospinal fluid (CSF). In a porcine model of global cerebral ischemia during CPB, we examined the presence of S-100 in the sagittal sinus after bypass and correlated serum and CSF S-100 levels. Methods: In an approved study, sagittal sinus catheters were placed in 40 anesthetized pigs. Animals were cannulated and placed on CPB. Baseline serum S-100 levels from the sagittal sinus were obtained. Electroencephalographic (EEG) signals from scalp needle electrodes assessed the severity of cerebral ischemia. All animals underwent 15 minutes of global cerebral ischemia produced by temporarily ligating the innominate and left subclavian arteries followed by reperfusion. Thirty minutes after discontinuing CPB, a needle was inserted into the cisterna magna to collect CSF; simultaneously, a sample of sagittal sinus blood was aspirated. S-100 protein contents were analyzed using a monoclonal immunoradiometric assay (Sangtec Medical, Sweden). Results: Cerebral ischemia was confirmed by total loss of EEG activity. Sagittal sinus S-100 levels at baseline were 0.09 +/- 0.06 [micro sign]g/L and increased significantly after ischemia (0.24 +/- 0.22 [micro sign]g/L; p<0.05). After bypass, CSF S100 levels were significantly greater than corresponding serum concentrations: 4.35 +/- 3.1 [micro sign]g/L (p<0.05). There was a weak linear correlation (r=0.37) between serum and CSF S-100 concentrations after CPB (p<0.02; Figure 1).Figure 1Discussion: Serum S-100 protein in the sagittal sinus increased significantly after ischemia, confirming the usefulness this assay to detect cerebral ischemic injury during CPB. However, the variable relationship between blood and CSF sites may indicate short-lived, reversible changes in blood-brain barrier permeability after ischemia on CPB. The amount of ischemic cerebral damage as measured by CSF S-100 protein concentration may not be reflected by serum S-100 values.

Relationships Between Plasma Leptin and Insulin Concentrations, But Not Insulin Resistance, in Non-insulin-Dependent (Type 2) Diabetes Mellitus

In non-diabetic subjects, insulin concentrations and insulin resistance are clearly connected, and both correlate with leptin levels, making interpretations about mechanisms difficult. In non-insulin-dependent (Type 2) diabetes mellitus (NIDDM), however, insulin concentrations and insulin resistance are less closely associated. Therefore, we examined the relationship of plasma leptin concentrations within insulin resistance and insulin levels in 32 subjects with NIDDM, who underwent measurement of insulin resistance with an insulin sensitivity test. Plasma leptin was measured with an in-house monoclonal immunoradiometric assay. Fasting leptin level correlated with BMI (r = 0.78; p < 0.001), metabolic clearance rate of glucose (= -0.44; p = 0.015), and fasting specific insulin (r = 0.58; p = 0.001), but not with age, cholesterol, triglycerides or blood pressure (r = -0.26 to 0.21; p = NS). In linear regression analysis, after adjustment for BMI and gender, leptin concentrations correlated with those of insulin (partial r = 0.42; p = 0.025), but not insulin resistance (partial r = -0.10; p = NS). We conclude that in NIDDM, concentrations of plasma leptin are closely related to those of insulin per se and to obesity, but not to insulin resistance. Insulin may be an important regulator of leptin concentration in NIDDM.

A two-site monoclonal antibody immunoradiometric assay for human follistatin: secretion by a human ovarian teratocarcinoma-derived cell line (PA-1).

The follistatin/activin/inhibin system increasingly appears to have important growth and differentiating effects in a variety of cell types, including cancer. We have developed a two-site immunoradiometric assay for measurement of human follistatin using two monoclonal antibodies against recombinant human follistatin. This cloned protein donor assay is sensitive (0.5 ng/mL), specific for free human follistatin, and precise (<5% within assay coefficient of variation). Using this assay, native human follistatin could be measured in human pituitary extracts, follicular fluid, and granulosa-luteal cell-conditioned medium. To identify and characterize human follistatin secreted by ovarian cancer cells, we screened five human ovarian carcinoma cell lines currently available from the American Type Culture Collection (Rockville, MD). One of these, a cell line derived from a teratocarcinoma (designated PA-1, American Type Culture Collection, CRL1572), secreted large (3 microg/10(6) cells per 24 h) quantities of immunoreactive follistatin constituitively. Increasing volumes of conditioned medium from these cultured cells generated response curves parallel to those of recombinant human follistatin 288 reference protein, human follicular fluid, or culture medium from human granulosa-luteal cells. Secretion of follistatin by PA-1 cells was time and cell-number dependent with 297.9 +/- 15.2, 654 +/- 29.8, and 940 +/- 49.1 ng follistatin secreted over 24 h by 1 x 10(5), 2 x 10(5), and 3 x 10(5) cells, respectively. Western and ligand blot analysis revealed that the immunoreactive follistatin secreted by PA-1 cells and isolated by sulfate-cellufine chromatography was identical to the molecular weight variants (32,000 and 35,000 Mr) of recombinant human follistatin 288. PA-1 cell-conditioned medium suppressed basal secretion of FSH by cultured rat anterior pituitary cells in a dose-dependent fashion. This follistatin bioactivity was completely removed by adsorption with either solid-phase monoclonal antifollistatin or a dextran-sulfate chromatography gel. Because activin suppressed the proliferation of PA-1 cells, secretion of bioactive follistatin may represent an autocrine mechanism opposing activin to maintain the rapid growth rate of PA-1 cells. These observations demonstrate that the ovarian teratocarcinoma cell line, PA-1, secretes considerable amounts of human follistatin that is biologically active, capable of binding human activin, and antigenically similar to recombinant human follistatin 288. The monoclonal antibodies and two-site assay reported herein should be useful in assessing the regulation of follistatin secretion and as a diagnostic tool, especially if follistatin measurements prove to be a marker for some ovarian cancers.

A two-site monoclonal antibody immunoradiometric assay for human follistatin: secretion by a human ovarian teratocarcinoma-derived cell line (PA-1)

A two-site monoclonal antibody immunoradiometric assay for human follistatin: secretion by a human ovarian teratocarcinoma-derived cell line (PA-1)

Microparticle Immunoenzymatic Assay for Detection of Prostate Specific Antigen: Characterization of the Technique and Comparative Analysis with a Monoclonal Immunoradiometric Assay

Microparticle immunoenzymatic assay (MEIA) is a new, ultrasensitive technique recently introduced for detection of prostatic specific antigen (PSA). It is easily performed, totally automated, and cheaper and faster than radioimmunometric techniques. In this study, the levels of PSA in 194 males with urologic problems and healthy males, recorded by microparticle monoclonal ultrasensitive enzymoimmunoassay (MEIA) and immunoradiometric assay (IRMA), are comparatively evaluated. Variables recorded were age of patient, size and weight of the prostate, and PSA levels analyzed by the MEIA (MEIA-PSA) and IRMA (ELSA-PSA) techniques. Different determinations of PSA were performed in order to calculate the intra- and interassay variation coefficient for the MEIA-PSA assay. Means of prostatic length, width, and depth, recorded by ultrasonography, were 28.3, 35.8, and 31.4 mm, respectively, with a mean prostatic size of 19 ml and a mean prostatic weight of 23.9 g. Mean IRMA-PSA was 4.53 ng/ml and mean MEIA-PSA was 2.04 ng/ml. The difference between them was 2.49, and the ratio IRMA-PSA:MEIA-PSA was 3.17. Interassay and intraassay variation coefficients for MEIA-PSA were 6.58 and 9.96%, respectively. MEIA-PSA values correlated linearly with the age of the patients (r = 0.65, p = 0.0001), size of the prostate (r = 0.71, p = 0.0001), weight of the prostate (r = 0.71, p = 0.0001), and the value of IRMA-PSA (r = 0.80, p = 0.0001). Paired t tests showed that the values of PSA measured by MEIA and IRMA are statistically different (p = 0.0001), with independence of the level of PSA considered.

Bone alkaline phosphatase in rheumatic diseases.

A double monoclonal immunoradiometric assay specific for bone alkaline phosphatase (BAP) was used to determine whether the raised total alkaline phosphatase (TAP) often found in patients with active rheumatoid arthritis (RA) and ankylosing spondylitis (AS) is derived from bone or liver. Fifty-eight patients with RA were compared to 14 with AS and 14 with non-inflammatory rheumatic diseases (NI). None had clinical liver disease and only one had a slightly elevated aspartate transaminase activity. Elevated BAP concentrations were found in seven patients (5 RA, 1 AS, 1 NI), only two of whom also had abnormal TAP. Abnormal TAP activities were found in only three patients (all RA). BAP did not correlate with disease activity in RA or AS. In contrast, TAP correlated with disease activity (assessed by plasma viscosity) in RA (P < 0.002) and gamma-glutamyl transferase (GGT) also correlated with plasma viscosity in RA (P < 0.01). Both TAP and BAP were significantly correlated with GGT in RA (P < 0.001 and P < 0.02, respectively). These findings are discussed, together with possible reasons for the conflicting nature of some of the observations.

Presence of hepatitis B and C viral genomes in US blood donors as detected by polymerase chain reaction amplification

Hepatitis C virus (HCV) represents a major cause of posttransfusion hepatitis worldwide. Posttransfusion hepatitis associated with hepatitis B virus (HBV) continues to occur. HBsAg-negative donor sera from the Rhode Island Blood Center between 1987 and 1988 were screened using more sensitive techniques to assess the prevalence of low level HBV infection. Group I consists of 866 healthy blood donors without HBV serologic markers, group II consists of 377 donors with ALT elevations (> 45 IU/L), group II consists of 148 donors positive for anti-HBc, and group IV consists of eight donors positive for both surrogate markers. A sensitive monoclonal immunoradiometric assay (M-IRMA) was employed for detection of HBsAg-associated epitopes (detection limit of 20 pg/ml) in serum. A subset of sera were analyzed for the presence of HBV DNA using the method of anti-HBs capture of HBV related virions in serum followed by polymerase chain reaction (PCR) amplification. Using these techniques, 0.8% and 1.7% of donors were positive for HBsAg and HBV DNA respectively in group I. In contrast, 0.9% and 9.5% in group II and 0.7% and 18.1% in group III were positive, respectively. There were eight donors with both ALT elevation and anti-HBc; and four (50%) of these were positive for HBV DNA. In the group with anti-HBc, the majority (80%) of donors with HBV DNA had either no or low (signal to noise ratio < 10) anti-HBs titer. Using anti-HCV testing and reverse transcription-PCR for detection of HCV genomes, we detected evidence of HCV infection in nine of the 49 donors with low level HBV DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of insulin-like growth factor-II in human plasma using a specific monoclonal antibody-based two-site immunoradiometric assay

An immunoradiometric assay (IRMA) for the measurement of insulin-like growth factor-II (IGF-II) in human plasma has been developed, optimized and evaluated clinically in normal subjects and patients with disorders of the GH/IGF-I axis. Six monoclonal antibodies (MAbs) to recombinant human IGF-II (rhIGF-II) were produced, all of which had low cross-reactivity with rhIGF-I (< 0.01%) and insulin (< 0.01%). Compatibility of pairs of MAbs was tested in two-site IRMAs using three radioiodinated MAbs and three MAbs linked to Sephacryl S-300 (with separation of bound and free radiolabelled MAb by sucrose layering). Seven pairs of MAbs bound rhIGF-II and the combination of 125I-labelled W3D9 and W2H1 linked to solid phase was selected. The optimized assay had a completion time of 4 h, a minimum detection limit of 30 ng/ml (2.5 standard deviations from the zero standard) and detected a single peak of endogenous IGF-II in normal plasma which co-eluted with rhIGF-II after acid gel chromatography. IGF-II was measured in formic acid/acetone extracts of plasma from 16 normal subjects (mean 685, range 516-1008 micrograms/l), four acromegalic patients (mean 637, range 553-700 micrograms/l), fourteen patients with type-1 diabetes (mean 635, range 247-753 micrograms/l), nine patients with uraemia (mean 423, range 78-850 micrograms/l), and three patients with Laron-type GH insensitivity (75, 35 and 36 micrograms/l). No significant fluctuations were detected between samples obtained hourly from 08.00 to 19.00 h in normal subjects. Low levels of IGF-binding proteins (IGFBPs) remaining in plasma extracts may interfere with the measurement of IGF-II and give rise to falsely elevated IGF-II levels in radioimmunoassays or falsely suppressed levels in IRMAs. Such interference did not occur with the IRMA when used to measure IGF-II in extracts from normal subjects, acromegalic patients and patients with type-1 diabetes, and the addition of excess rhIGF-I in order to displace IGF-II from residual IGFBPs had no effect on IGF-II measurements in these samples. However, levels of IGF-II measured in extracts from patients with Laron-type GH insensitivity and patients with uraemia increased markedly after preincubation with excess rhIGF-I. The accurate measurement of IGF-II by IRMA in extracts from these subjects therefore requires the displacement of IGF-II from IGFBPs prior to assay. We conclude that, in contrast to radioimmunoassays, the two-site IRMA developed here provides a practical, rapid and specific method for the measurement of IGF-II in human plasma.

Proopiomelanocortin is the predominant adrenocorticotropin-related peptide in human cerebrospinal fluid.

High mol wt forms of immunoreactive ACTH and beta-endorphin (beta EP) are present in cerebrospinal fluid (CSF). We have quantified these peptides directly in the CSF of 26 patients undergoing routine myelography, using a panel of monoclonal antibody-based two-site immunoradiometric assays, specific for ACTH precursors (both POMC and pro-ACTH cross-react 100%), POMC, ACTH, and beta EP. The mean +/- SD levels of POMC in CSF were 530 +/- 150 pmol/L similar to total ACTH precursor immunoreactivity (414 +/- 83 pmol/L). By comparison, the CSF levels of ACTH (3.2 +/- 0.6 pmol/L) and beta EP (6.7 +/- 2.9 pmol/L) were 100-fold lower. POMC, by virtue of its 1% cross-reactivity in the ACTH immunoradiometric assay, could have also accounted for the ACTH immunoreactivity in CSF. Sephadex G-75 chromatography of CSF confirmed the presence of a single major peak of ACTH precursors eluting at the position of POMC (31K), while ACTH immunoreactivity was not detected at the position of ACTH-(1-39) (4.5K). We also studied the effect of exogenous glucocorticoids on CSF POMC peptides by giving 2.5 mg dexamethasone (0.5 mg, orally, every 6 h for 24 h) to a similar group of age-matched patients before lumbar puncture. No significant differences in CSF peptide content were observed between the two groups. These data suggest that the unprocessed precursor molecule POMC is the predominant peptide of the POMC family in human CSF and should always be considered when interpreting data involving ACTH or other component peptide immunoreactivity in this biological fluid.

High serum procalcitonin concentrations in patients with sepsis and infection

High concentrations of calcitonin-like immunoreactivity have been found in the blood of patients with various extrathyroid diseases. By means of a monoclonal immunoradiometric assay for calcitonin precursors, we have measured serum concentrations of procalcitonin in patients with various bacterial and viral infections. 79 children (newborn to age 12 years) in hospital with suspected infections were investigated prospectively. 19 patients with severe bacterial infections had very high serum concentrations of procalcitonin at diagnosis (range 6-53 ng/mL) in comparison with 21 children found to have no signs of infection (baseline concentrations <0·1 ng/mL). Serum procalcitonin values decreased rapidly during antibiotic therapy. 11 patients with peripheral bacterial colonisation or local infections without invasive sepsis and 18 (86%) of 21 patients with viral infections had concentrations within or slightly above the normal range (0·1-1·5 ng/mL). Among 9 severely burned patients studied in an intensive care unit, the post-traumatic course of procalcitonin concentrations (range 0·1-120 ng/mL) was closely related to infectious complications and acute septic episodes. Concentrations of mature calcitonin were normal in all subjects, whatever procalcitonin concentrations were found. Concentrations of a substance immunologically identical to procalcitonin are raised during septic conditions. Serum concentrations seem to be correlated with the severity of microbial invasion.

Standardization with Synthetic 22-KDa Monomer Human Growth Hormone Reduces Discrepancies Between Two Monoclonal Immunoradiometric Assay Kits

Discrepancies among different methods for assaying human growth hormone have been described in various studies. The two major sources of discordant results are the heterogeneity of the antibodies and the different standardization bases used by the assay manufacturers. We propose standardizing assays with 22-kDa biosynthetic monomer human growth hormone diluted with the diluents supplied by the kit manufacturers. In a study of two monoclonal immunoradiometric assays (Hybritech, specific for the 22-kDa monomer; Sorin, recognizing also a 20-kDa variant hormone), standardization with 22-kDa monomer human growth hormone reduced by 63% the differences in results for 44 serum samples from children. The use of 22-kDa human growth hormone as a common standard, highly pure and easily available in large quantities, could help limit the interpretative problems in growth diagnostics.

Two-Site Monoclonal Antibody-Based Immunoradiometric Assay for Measuring Prostate Secretory Protein in Serum

We developed a double-determinant immunoradiometric assay for measuring serum prostate secretory protein (PSP), using monoclonal antibodies (MAb) against two different epitopes: MAb PSP-19 was the capture antibody and MAb PSP-6 was the tracer antibody. Assay sensitivity was 0.1 microgram/L. Analytical recovery of PSP was 93.5-104.6%, whereas the intra- and interassay mean CVs were 4.2% and 6.9%, respectively. In 92 normal men, ages greater than 50 years, the mean PSP concentration was 5.7 micrograms/L, with 10 (10.9%) men having concentrations greater than 10 micrograms/L. In contrast, 20 of 49 (40.8%) patients with benign prostate hyperplasia (BPH; mean PSP concentration 9.4 micrograms/L) and 46 of 100 (46%) patients with prostate cancer (mean PSP concentration 22.2 micrograms/L) had PSP concentrations greater than 10 micrograms/L. Mean serum PSP concentrations of the BPH (P less than 0.05) and prostate cancer (P less than 0.01) groups were significantly different from those of age-matched normal men. In a small group of patients, serial PSP concentrations correlated with the clinical course during therapy. Thus, PSP may be a useful marker for evaluating patients with prostate cancer.

Reliability of Stimulated and Spontaneous Growth Hormone (GH) Levels for Identifying the Child with Low GH Secretion

The reliability of stimulated and spontaneous GH levels for identifying the child with low GH secretion has been the subject of debate. We compared the ability of GH concentrations after pharmacological stimulation with levodopa and clonidine and of spontaneous peak and 12-h pooled GH concentrations during sleep on a single night to estimate the maximum spontaneous GH secretion from 2 nights in 55 children, aged 5–16 yr, with heights below the 3rd percentile and/or height velocities below the 25th percentile for age, who had two consecutive overnight GH secretory profiles. Maximum stimulated GH concentrations correctly categorized 80% of children who had maximum spontaneous GH concentrations above and below 4 μg/L using a double monoclonal immunoradiometric assay for GH (Tandem-R HGH, Hybritech). The remaining 20% of children had stimulated GH concentrations below but spontaneous GH concentrations above 4 μg/L. Using this cut-off, the maximum GH concentrations from the first and second nights correctly ca...

Maternal Serum CA125 is Not a Second Trimester Marker for Down's Syndrome

Check et ul.’ reported in 1990, three women with very elevated, early first trimester CA125 concentrations, who subsequently spontaneously aborted in the late first or early second trimester, and in whom the products of conception showed chromosomal abnormalities (Trisomy 12 and 13, 45X, Trisomy 21). Check et al.’ concluded that a high maternal serum CAl25 concentration might be predictive of an abnormal karyotype. Following this initial observation I have considered the possibility that CA125, if truly an indicator of abnormal karyotype, may still be elevated in viable second trimester pregnancies. Furthermore, if this was the case, then it might prove to be a useful screening test for Down’s syndrome (Trisomy 21) or as an adjunct to other serological marker^.^,^ In order to test the hypothesis, 25 maternal serum samples from Down’s syndrome pregnancies were identified from stores of abnormal samples, along with five unaffected control cases for each Down’s case. The controls were matched for gestational age (k 3 days), maternal age (k 6 months) and a length of storage (k 1 month). A further series of samples, covering the gestational age range 16-20 weeks, were chosen at random from our pool of normal singleton pregnancies. An additional series of samples was identified in which the pregnancy ended in intra uterine death (10 cases) or spontaneous abortion (10 cases). All samples were analysed for CA125 using a solid phase two site monoclonal immunoradiometric assay (ELSA-CA125, CIS (UK) Ltd, High Wycombe, UK) according to the manufacturer’s protocol. Since there is no International Standard for CA125, the results were expressed in arbitrary units (U/mL) as determined by the kit manufacturer. The samples were spread evenly over five different assay batches and the between assay precision was found to be 3.8% coefficient of variation at 119 U/mL and 8.2% at 20 U/mL. To allow for possible variation in CA125 levels with gestational age, all values were expressed as multiples of the median (MOM) value for unaffected pregnancies of the same gestational age. Table 1 summarizes the data showing the variation of CA125 with gestational age. The data showed only minor variation; only the change from 16 to 17 weeks being possibly statistically significant ( 0 . 0 5 > P > 0 . 0 2 ) using t tests of significance. The combined median for all the normal data (n = 231) was 19.4 U/mL. There was no correlation of CA125 with maternal age (r=0.00199) .