Two alpha-chain hemoglobin variants, Hb Broussais and Hb Cemenelum, characterized by cation-exchange HPLC, isoelectric focusing, and peptide sequencing

We here report the characteristics of two rare alpha-chain hemoglobin (Hb) variants. The variants were found during quantification of HbA1c by cation-exchange HPLC with the Diamat glycohemoglobin analyzer. They were further characterized by isoelectric focusing and PolyCAT A cation-exchange chromatography. The structure of the abnormal Hbs was established by amino acid analysis after separation of the globin chains by reversed-phase chromatography, digestion with trypsin, separation of the peptides by reversed-phase chromatography, and amino acid sequencing. These studies showed that the two variants were Hb Broussais [alpha 90 (FG2)Lys-->Asn] and Hb Cemenelum [alpha 92 (FG4)Arg-->Trp].

Age-related course of urinary gonadotropins in children

Serum levels of LH and FSH are very low from about 2 yr of age to the onset of puberty, which is heralded by a very sharp increase in LH levels. We studied age-related changes in urinary gonadotropins in a total of 184 boys and girls of various ages. Urinary FSH and LH were measured by ultrasensitive time-resolved immunofluorometric assays. The detection limit was 0.015 IU/L for LH and 0.018 IU/L for FSH. We observed that after an initial drop following the first months of life, urinary LH levels stayed below 0.5 IU/L until age 9 yr in girls and below 1.0 IU/L until age 11 yr in boys, whereas mean urinary FSH levels remained below 3.0 IU/L until age 10 yr in girls and 12 yr in boys. During puberty, mean urinary FSH and LH concentrations increased to about 5 IU/L in boys and 10 IU/L in girls. This corresponds to a 5-fold increase in FSH in both sexes and a 50- to 100-fold increase in LH in boys and girls, respectively. These dynamic changes agree with previous reports regarding serum levels, suggesting that noninvasive urinary gonadotropin measurements can be a viable alternative to serum determinations in the evaluation of gonadotropin secretion during childhood and adolescence.

Two alpha-chain hemoglobin variants, Hb Broussais and Hb Cemenelum, characterized by cation-exchange HPLC, isoelectric focusing, and peptide sequencing

We here report the characteristics of two rare alpha-chain hemoglobin (Hb) variants. The variants were found during quantification of HbA1c by cation-exchange HPLC with the Diamat glycohemoglobin analyzer. They were further characterized by isoelectric focusing and PolyCAT A cation-exchange chromatography. The structure of the abnormal Hbs was established by amino acid analysis after separation of the globin chains by reversed-phase chromatography, digestion with trypsin, separation of the peptides by reversed-phase chromatography, and amino acid sequencing. These studies showed that the two variants were Hb Broussais [alpha 90 (FG2)Lys-->Asn] and Hb Cemenelum [alpha 92 (FG4)Arg-->Trp].

Habitual abortion is accompanied by low serum levels of placental protein 14 in the luteal phase of the fertile cycle

OBJECTIVE

To study serum levels of placental protein 14 (PP14) in relation to endometrial function in women with a history of habitual abortion.

DESIGN

Prospective study.

SETTING

Departments I and II of Obstetrics and Gynecology, University Central Hospital of Helsinki, Helsinki, Finland.

PATIENTS

Fifty patients (26 primary and 24 secondary habitual aborters) and 38 controls without a history of abortion studied during a regular cycle.

RESULTS

Habitual aborters as a whole or when subgrouped into those with normal cycles (n = 40) or with a luteal phase defect (LPD; n = 10) and control women demonstrated a distinct increase in PP14 levels from late follicular to late luteal phases. In the luteal phase, serum PP14 levels were lower in the patients than in the controls (27.2 +/- 3.1 versus 48.5 +/- 10.1 micrograms/L), but the differences in PP14 levels between habitual aborters with or without LPD was not significant (16.3 +/- 4.3 versus 29.9 +/- 3.7 micrograms/L).

CONCLUSIONS

Habitual aborters exhibit lower serum PP14 levels in the late luteal phase compared with normal fertile women.

Detection of prostatic cells in peripheral blood: correlation with serum concentrations of prostate-specific antigen

We have studied the expression of prostate-specific antigen (PSA) mRNA by reverse transcriptase-polymerase chain reaction in peripheral blood of 25 patients with cancer of the prostate (CAP), four with benign prostatic hyperplasia (BPH), two with renal stones, three with other types of cancer, and six healthy male and three female controls. Expression of mRNA specific for a certain tissue in peripheral blood is thought to indicate the presence of circulating cancer cells and metastatic spread of a tumor originating from this tissue. We detected PSA mRNA in 9 of 18 CAP patients with metastatic disease but in none of 7 patients without metastases. Negative results in patients with metastatic disease were associated with successful endocrine therapy and low concentrations of serum PSA, and the correlation between serum concentrations of PSA and the presence of PSA mRNA in peripheral blood was statistically significant. PSA mRNA was not found in patients with BPH, other types of cancer, or in healthy controls. Thus the occurrence of PSA mRNA in peripheral blood is associated with metastatic CAP.

Three assays for glycohemoglobin compared

Using 123 specimens, we compared the concordance of three different methods for determining glycohemoglobin (GHb): the Diamat (Bio-Rad Laboratories), an automated analyzer measuring HbA1c by cation-exchange chromatography; an assay with the IMx analyzer (Abbott Laboratories), based on boronate affinity binding; and an HPLC method measuring HbA1c by cation-exchange chromatography on a PolyCAT A column (PolyLC Inc.). The Pearson's correlation coefficient between PolyCAT A and Diamat was 0.900 +/- 0.038 (mean +/- 2 SD) and between PolyCAT A and IMx, 0.857 +/- 0.042. However, up to twofold differences were seen in some samples. The proportion of GHb was consistently lower with the PolyCAT A method than with the other two assays, apparently because of better separation of HbA1c from nonglycated coeluting forms of Hb. The difference in glycation percentage between the PolyCAT A and Diamat methods is 2-3% over the whole concentration range. These results point to the limitations of Diamat as a reference method to be used to calibrate other methods for determining HbA1c. Further, a switch from one method to another is likely to cause considerable problems in the clinical follow-up of certain patients.

Detection of prostatic cells in peripheral blood: correlation with serum concentrations of prostate-specific antigen

We have studied the expression of prostate-specific antigen (PSA) mRNA by reverse transcriptase-polymerase chain reaction in peripheral blood of 25 patients with cancer of the prostate (CAP), four with benign prostatic hyperplasia (BPH), two with renal stones, three with other types of cancer, and six healthy male and three female controls. Expression of mRNA specific for a certain tissue in peripheral blood is thought to indicate the presence of circulating cancer cells and metastatic spread of a tumor originating from this tissue. We detected PSA mRNA in 9 of 18 CAP patients with metastatic disease but in none of 7 patients without metastases. Negative results in patients with metastatic disease were associated with successful endocrine therapy and low concentrations of serum PSA, and the correlation between serum concentrations of PSA and the presence of PSA mRNA in peripheral blood was statistically significant. PSA mRNA was not found in patients with BPH, other types of cancer, or in healthy controls. Thus the occurrence of PSA mRNA in peripheral blood is associated with metastatic CAP.

Markers supplementing CA 125 in ovarian cancer

Markers supplementing CA 125 are important for monitoring of the disease in patients with mucinous and non-epithelial ovarian cancers. Tumour-associated trypsin inhibitor (TATI) or one of the gastrointestinal mucin markers, CA 19-9 or CA 72.4 are good supplements to CA 125 in mucinous ovarian cancer. Chorionic gonadotrophin (hCG) and alpha fetoprotein (AFP) are the most useful markers for germ cell tumours, and hCG beta may provide additional information. In addition to hCG beta, M-CSF and inhibin show promise of becoming useful supplements to CA 125 in ovarian cancer in general. Markers other than CA 125 may also play a role as prognostic indicators. TATI and procollagen peptides appear useful for this purpose. If these markers prove to provide reliable prognostic information, they could be used to aid selection of optimal treatment regimens.

Standardization of PSA determinations

Standardization of determinations for prostate specific antigen (PSA) has become an important issue due to the widespread use of these determinations for prostate cancer screening. Standardization of this assay is complicated due to the occurrence of two major forms of PSA in serum, the free antigen and a complex between PSA and alpha 1-antichymotrypsin (PSA-ACT). These two forms of PSA are recognized differently by different antibodies, but by careful selection of antibodies, it is possible to design methods that measure each form equally. It is suggested, that standards for PSA and PSA-ACT should be prepared and established as international standards. Furthermore, reference methods should be established on the basis that these standards and carefully selected reference antibodies.

Serum concentrations of prostate specific antigen and its complex with alpha 1-antichymotrypsin before diagnosis of prostate cancer

Prostate cancer can be detected at an early, potentially curable stage by screening based on digital rectal examination and serum prostate specific antigen (PSA). The value of screening appears doubtful, based on high 10-year survival rates in selected cases of early prostate cancer, but this follow-up time may be insufficient. By linking the information on 21172 men who took part in a screening examination in Finland, 1968-73, with data from the Finnish Cancer Registry, 44 cases of prostate cancer diagnosed up to 1980 were identified. Serum samples from cancer cases and from 74 controls matched for age and time of sampling were assayed for PSA and its complex with alpha 1-antichymotrypsin (PSA-ACT). With a cut-off for PSA of 2.5 micrograms/L giving 92% specificity, 95% of the cancers developing within the first 5 years, and 52% developing in 6-10 years tested positive. As a potential screening test with a 5-year interval for men under 65, the sensitivity would be 92% and specificity 97%. The ratio of PSA-ACT to total PSA was lower in controls than in patients with cancer. Using this ratio, we could eliminate half of the false-positive results in the range 2.5-25 micrograms/L without loss of sensitivity. Cancer was typically diagnosed 5-10 years after PSA exceeded 2.5 micrograms/L, and the median survival after diagnosis was 3.6 years. 10-year survival after drawing the sample was 71% in cancer cases with a PSA concentration less than 4 micrograms/L and 48% in those with higher concentrations. The corresponding figures at 15 years were 53% and 27%, and at 20 years 43% and 18%, respectively. These results suggest it is advisable to confine screening for prostate cancer to men with a life expectancy of clearly more than 10 years--ie, younger men, who have the greatest chance to benefit from early detection.

Tumour-associated trypsin inhibitor (TATI): comparison with CA125 as a preoperative prognostic indicator in advanced ovarian cancer

We have evaluated the prognostic value of tumour-associated trypsin inhibitor (TATI) in stage III or IV ovarian cancer. Tumour-associated trypsin inhibitor (TATI) and CA 125 were determined in serum samples from 66 patients taken before primary surgery. TATI was elevated (> 22 micrograms l-1) in 27 patients (41%). These had a 5 year cumulative survival of 8%, whereas survival was 45% in 39 patients with normal preoperative TATI values. By contrast, the preoperative CA 125 level did not predict survival. In multivariate analysis which included age, stage, histological grade and preoperative TATI and CA 125 levels, patients with elevated preoperative TATI levels had a 2.3-fold relative risk of death (95% confidence interval 1.23-4.20; P = 0.002) compared with patients with normal preoperative levels. This result was comparable with the predictive value of primary residual tumour size, since patients with residual tumour larger than 2 cm in diameter had a 5.2-fold relative risk of death (95% confidence interval 2.55-10.68) compared with patients with a smaller or no residual tumour. Thus, preoperative determination of serum TATI may have a place in the pretreatment evaluation of patients with advanced ovarian cancer.

Streptavidin-biotin based time-resolved immunofluorometric assay for direct measurement of high concentrations of human chorionic gonadotropin (hCG)

Quantitation of human chorionic gonadotropin (hCG) in maternal serum is widely used for screening of fetal trisomy-21 (Down's syndrome). When using immunometric assay, the sample usually has to be prediluted in order to quantitate the high hCG concentrations occurring during weeks 10-17 of pregnancy. Utilizing a streptavidin-biotin system we have developed an immunofluorometric assay (IFMA) for the quantitation of hCG in pregnancy serum that does not require predilution of the sample. The sample is added to a streptavidin coated microtiter strip well together with a biotinylated 'capture' antibody. About 1-2% of the capture antibody is biotinylated whereas most of the antibodies are unbiotinylated and thus unable to bind to the solid phase, while still binding antigen. This displaces the assay range from 0.5-5000 IU/l of the standard assay to 20-250,000 IU/l. The method shows good correlation with the standard procedure (r = 0.96). By eliminating a dilution step the assay procedure is both simplified and reinforced. The principle of this method should be readily applicable to other antigens and detection methods.

Determination of human tumour necrosis factor-alpha (TNF-alpha) by time-resolved immunofluorometric assay

We have developed a 'sandwich'-type time-resolved immunofluorometric assay (IFMA) for tumour necrosis factor alpha (TNF-alpha) using two monoclonal antibodies (mAb) and the streptavidin/biotin (SAB) system. In this simple and fast streptavidin/biotin IFMA (SAB-IFMA) we used streptavidin coated wells to which we added biotinylated mAb for 3 h. After washing, the serum sample was added and incubated for 2 h followed by washing. Another monoclonal europium-labelled tracer antibody was added and incubated for 1 h, the wells were washed and the fluorescence of Eu measured. We tested various assay conditions in order to optimize the assay for sensitivity and measuring range. Purification of the labelled antibody by hydrophobic interaction chromatography was found to be essential to improve sensitivity. With a sample volume of 50 microliters the detection limit was 6 ng l-1 and the analytical range large, i.e. 10,000-fold. The median concentration in serum from healthy subjects was 12 ng l-1 and the reference range < 39 ng l-1. The mean analytical recovery in plasma was 76% and in serum 83%. Separation of serum by gel filtration and assay of TNF-alpha in fractions showed that the assay also measured the high molecular weight (MW) form of TNF-alpha, apparently corresponding to its complex with soluble receptors. Advantages of our SAB-IFMA were high sensitivity and low consumption of mAb. The assay performance of the SAB-IFMA was compared to two commercially available enzyme immunoassays also using the SAB system.

Time-resolved immunofluorometric assay of trypsin-2 complexed with alpha 1-antitrypsin in serum

We developed a sensitive time-resolved immunofluorometric assay (IFMA) for trypsin-2 complexed with alpha 1-antitrypsin (AAT). We used a trypsin-2-specific monoclonal antibody on the solid phase and a europium-labeled polyclonal antibody to AAT as tracer. The detection limit is 0.05 microgram/L and the range of linearity extends to 100 micrograms/L. We compared the clinical utility of the trypsin-2-AAT assay with that of free trypsinogen-2 and amylase in serum by studying 120 healthy subjects, 29 patients with acute pancreatitis, 11 with extrahepatic biliary obstruction, and 34 with acute abdominal disorders of extrapancreatic origin. In patients with acute pancreatitis the median concentration of trypsin-2-AAT in serum was 59-fold that in healthy controls, 42-fold that in patients with biliary obstruction, and 33-fold that in patients with acute abdominal disorders of extrapancreatic origin. These differences are greater than those for trypsinogen-2 (19-, 20-, and 28-fold, respectively) and amylase (5.4-, 6.5-, and 5.4-fold, respectively). Compared with the assays of free trypsinogen-2 and amylase, our assay of trypsin-2-AAT improved the clinical specificity for acute pancreatitis by eliminating false-positive results in our control groups. Increased concentrations of trypsin-2-AAT and trypsinogen-2 were also observed in patients with chronic renal failure undergoing dialysis.

Time-resolved immunofluorometric assay of trypsin-2 complexed with alpha 1-antitrypsin in serum

We developed a sensitive time-resolved immunofluorometric assay (IFMA) for trypsin-2 complexed with alpha 1-antitrypsin (AAT). We used a trypsin-2-specific monoclonal antibody on the solid phase and a europium-labeled polyclonal antibody to AAT as tracer. The detection limit is 0.05 microgram/L and the range of linearity extends to 100 micrograms/L. We compared the clinical utility of the trypsin-2-AAT assay with that of free trypsinogen-2 and amylase in serum by studying 120 healthy subjects, 29 patients with acute pancreatitis, 11 with extrahepatic biliary obstruction, and 34 with acute abdominal disorders of extrapancreatic origin. In patients with acute pancreatitis the median concentration of trypsin-2-AAT in serum was 59-fold that in healthy controls, 42-fold that in patients with biliary obstruction, and 33-fold that in patients with acute abdominal disorders of extrapancreatic origin. These differences are greater than those for trypsinogen-2 (19-, 20-, and 28-fold, respectively) and amylase (5.4-, 6.5-, and 5.4-fold, respectively). Compared with the assays of free trypsinogen-2 and amylase, our assay of trypsin-2-AAT improved the clinical specificity for acute pancreatitis by eliminating false-positive results in our control groups. Increased concentrations of trypsin-2-AAT and trypsinogen-2 were also observed in patients with chronic renal failure undergoing dialysis.

Estrogen replacement does not potentiate gonadotropin-releasing hormone agonist-induced androgen suppression in treatment of hirsutism

The therapies presently available for treating ovarian hirsutism are not uniformly effective, and therefore, much has been expected from GnRH agonists. These inhibit the secretion of gonadotropins and thereby suppress ovarian function, but at the same time cause hypoestrogenic side-effects. We, therefore, administered goserelin, a long-acting GnRH agonist, for treatment of 20 hirsute women (18 with polycystic ovaries) for 9 months; half of them were randomized to receive cyclic estradiol and medroxyprogesterone replacement from the fourth month onward. Seventeen patients completed the study. Goserelin suppressed ovarian function, as evidenced by a profound reduction in serum estradiol levels. The circulating levels of total testosterone, free testosterone, and androstenedione were lowered at 3 months by 29%, 31%, and 38%, respectively, but there was no effect on the levels of sex hormone-binding globulin (SHBG) or dehydroepiandrosterone sulfate. Ovarian suppression, maintained for the duration of the trial, alleviated hirsutism, as evidenced by a decrease in Ferriman-Gallwey hirsutism scores. Estrogen plus progestin replacement restored estradiol levels and increased SHBG levels, but did not potentiate the therapeutic effect of goserelin or reduce free testosterone levels. Replacement therapy abolished or alleviated hypoestrogenic vasomotor symptoms, but it also caused bleeding and premenstrual symptoms, which necessitated the withdrawal of 3 of 10 women from the treatment. Thus, goserelin is an effective treatment for ovarian hyperandrogenism. Simultaneous estrogen replacement abolishes the hypoestrogenic side-effects, but does not potentiate the effect of goserelin on hirsutism. Interestingly, the estrogen-induced increase in SHBG did not affect free testosterone. Thus, the suppression of gonadotropins, rather than the increase in SHBG, appears to be of primary significance in the alleviation of ovarian hyperandrogenism by estrogens.

A clinically useful method for detecting gonadotropins in children: assessment of luteinizing hormone and follicle-stimulating hormone from urine as an alternative to serum by ultrasensitive time-resolved immunofluorometric assays

To study the feasibility of noninvasive sampling in pediatric patients, we examined the concentrations of LH and FSH in paired serum and urine samples from 65 children (age 0-15 y) with highly sensitive time-resolved immunofluorometric assays. The detection limits of the assays were 0.015 IU/L for LH and 0.018 IU/L for FSH. These sensitivity levels allowed quantification of the low prepubertal LH and FSH concentrations. The correlation between serum and urine gonadotropin values was very good (r = 0.751, p < 0.001 for FSH; and r = 0.720, p < 0.001 for LH), and the urine and serum concentrations were very similar. Correction of urinary gonadotropin concentrations for changes in urinary flow by standard methods using density [concentration x (0.02/density-1)] or creatinine (concentration/creatinine) did not improve the correlation. Therefore, measurement of urinary gonadotropins without correction can simply be used in the pediatric outpatient setting as a noninvasive alternative to serum determinations.

Evidence for involvement of BRCA1 in sporadic breast carcinomas

The hereditary breast cancer gene BRCA1 previously has been localized to chromosome 17q21. We looked for evidence of involvement of this region of chromosome 17 in 130 sporadic breast cancers. Seventeen polymorphic sequence tagged site markers were examined in these tumors between the D17S250 and D17S579 loci to screen for deletions as measured by loss of heterozygosity. The smallest common region that was deleted occurred in the approximately 120-kilobase interval between the D17S846 and D17S746 loci within the BRCA1 region. Delineation of this commonly deleted area should accelerate attempts to identify the involved gene(s) and its relationship to BRCA1.

Serum human chorionic gonadotropin dynamics during spontaneous resolution of ectopic pregnancy

OBJECTIVE

To study serum hCG dynamics in patients with ectopic pregnancy (EP) selected for expectant management.

DESIGN

A prospective observational study.

SETTING

Helsinki University Central Hospital, Helsinki, Finland.

SUBJECTS

One hundred eighteen patients, who were selected for expectant management among 493 patients with EP.

INTERVENTIONS

Patients were examined every 1 to 3 days using transvaginal sonography and serum hCG determinations until hCG values < 10 IU/L (conversion factor to SI unit, 1 IU/L = 2.93 pmol/L) were reached. Laparoscopy was performed if the patient developed abdominal pains or intra-abdominal hemorrhage as revealed by sonography.

MAIN OUTCOME MEASURE

Serum hCG level.

RESULTS

The median gestational age at the start of follow-up in patients with a spontaneous resolution was 44 days and in patients requiring laparoscopy was 48 days. The success rate for a spontaneous resolution was 88% when the initial hCG level was < 200 IU/L but only 25% at levels > 2,000 IU/L. In the 77 patients with a spontaneous resolution, the initial median hCG concentration was 374 IU/L (range, 20 to 10,762 IU/L) and it decreased to normal in 4 to 67 days (mean, 20 days). In the 41 patients requiring laparoscopy the median initial hCG concentration was 741 IU/L (range, 165 to 14,047 IU/L); a normal level was reached in 3 to 43 days (mean, 12 days) after operation. Follow-up period before operation was 1 to 24 days (mean, 9 days). Laparoscopy was indicated in two thirds of the patients with a serum hCG level > 64% of the initial value after 7 days of follow-up.

CONCLUSIONS

Spontaneous resolution of EP correlated with a low and rapidly decreasing hCG level.

Early screening for ectopic pregnancy in high-risk symptom-free women

We screened 225 symptom-free pregnant women at increased risk for ectopic pregnancy with transvaginal sonography and human chorionic gonadotropin (hCG) assays. Among 55 (24.4%), who proved to have an ectopic pregnancy, 46 (84%) cases were diagnosed at the initial screening at a median of 37 days of gestation, and the rest at repeated scans. The false-positive rate was 1.2%. Early diagnosis prevented tubal rupture, substantial haemorrhage, and the need for emergency care, allowing elective treatment. Such early surveillance reduced the risk of complications and facilitated treatment, and should be offered to at-risk women.

Tumour markers and screening for gastrointestinal cancer: a follow up study in Finland

BACKGROUND

Screening for gastrointestinal cancer is based mainly on a barium contrast x ray method and on identification of occult blood in stools. The methods are relatively expensive, not always acceptable to the participants, and there is only limited evidence of their effectiveness in reducing the mortality from gastrointestinal cancer.

OBJECTIVE

To investigate the validity of several tumour markers as a screening test for stomach cancer and for colorectal cancer.

METHODS

A registry of 36,265 serum samples drawn during 1968-72 was linked to the cancer registry. Follow up was during 1968-80 when 94 stomach cancers and 95 colorectal cancers were identified. One to two matched case-control design was applied, and the concentrations of CEA, CA 19-9, CA 50, and TATI were assessed.

RESULTS

The mean values of the markers between the cases and the controls were almost the same for the total material. Case-control differences were found between the 11 sets with an interval of less than one year between drawing the sample and diagnosis of the cancer. The highest validity was found in CEA for colorectal cancer (specificity 91%; sensitivity 64%) and in CA 19-9 for stomach cancer (specificity 74%; sensitivity 73%).

CONCLUSION

CEA, CA 19-9, CA 50, or TATI are not valid screening tests. Case-control differences were found with a potential one year screening interval, but they were not large enough for sufficient validity.

A new simple and rapid dual assay for AFP and free beta hCG in screening for Down syndrome

We have evaluated a simple and rapid 2-step dual-label assay (DELFIA) for alphafetoprotein (AFP) and free beta subunit of human gonadotropin (hCG beta) in second-trimester screening for Down syndrome. Based on stored serum samples from 1059 normal control pregnancies and 72 cases of Down syndrome, we have found the mean Multiple of Median (MoM) for AFP and free hCG beta to be 0.70 and 2.31, respectively. This is slightly but not significantly better than the values for the separate assay for AFP (0.76 MoM) and for intact hCG (2.11 MoM). However, the dual assay is much simpler than the separate assays and therefore prospective comparison trials should be carried out.

Aging is associated with decreased suppression of insulin-like growth factor binding protein-1 by insulin

We determined whether aging influences circulating insulin-like growth factor-binding protein-1 (IGFBP-1) concentrations and, if so, whether this effect is explained by altered regulation of IGFBP-1 by insulin. Fasting levels of glucose, insulin, and IGFBP-1 were measured in 94 healthy volunteers, ages 24-93 yr. To determine the effect of aging on insulin-induced suppression of IGFBP-1, an oral glucose tolerance test (OGTT) was performed in 10 older (72-92 yr) and 10 younger (24-58 yr) nonobese subjects, matched for sex and body mass index. For all ages combined, the mean glucose level (+/- SE) averaged 4.9 +/- 0.1 mmol/L, and there was no significant change with aging. Fasting insulin and IGFBP-1 concentrations increased with advancing age (r = 0.37, P < 0.001 for age vs. insulin and r = 0.47, P < 0.001 for age vs. IGFBP-1). However, there was no correlation between insulin and IGFBP-1 concentrations. In multiple linear regression analysis, the age-related increase in IGFBP-1 was independent of body mass index. During the OGTT, the mean insulin concentration was significantly higher in the older group compared with the younger group (P < 0.001). Serum IGFBP-1 concentrations were higher in the fasting state as well as during the OGTT, and the mean percent decrease of IGFBP-1 below baseline was significantly smaller in the older compared to the younger subjects at 3 h (35 +/- 5% vs. 55 +/- 2%, P < 0.01). We conclude that aging is associated with decreased suppression of serum IGFBP-1 by insulin, as demonstrated by 1) lack of the inverse correlation between fasting insulin and IGFBP-1 seen in young adults; 2) concurrent elevation of fasting insulin and IGFBP-1 concentrations; and 3) a blunted decrease in serum IGFBP-1 during an OGTT.

Simultaneous assay of alpha-fetoprotein and free beta subunit of human chorionic gonadotropin by dual-label time-resolved immunofluorometric assay

We developed a simple, rapid two-step dual-label assay for the noncompetitive determination of alpha-fetoprotein (AFP) and beta subunit of human chorionic gonadotropin (hCG beta) in serum. Monoclonal antibodies to detect AFP and hCG beta were labeled with europium (Eu) and samarium (Sm), respectively. Highly fluorescent chelates were developed by using the Delfia enhancement principle. The detection limits for AFP and hCG beta were approximately 0.02 kIU/L and approximately 0.2 IU/L, respectively. The within-run precision was < 5% over the whole range of AFP (1-500 kIU/L) and hCG beta (1-200 IU/L) concentrations tested. Cross-reaction of intact hCG was < 0.03%. The AFP concentrations determined with the dual-label assay correlated well with those obtained by Delfia AFP single-label kit. The concentrations of hCG beta were in good agreement with recently published data. Storing the serum samples for 24 h or 1 week at room temperature increased the hCG beta concentration by 4% and 26%, respectively. At 35 degrees C this dissociation of hCG increased 30-40-fold. Repeated freezing and thawing had no effect on the hCG beta concentration.

Simultaneous assay of alpha-fetoprotein and free beta subunit of human chorionic gonadotropin by dual-label time-resolved immunofluorometric assay

We developed a simple, rapid two-step dual-label assay for the noncompetitive determination of alpha-fetoprotein (AFP) and beta subunit of human chorionic gonadotropin (hCG beta) in serum. Monoclonal antibodies to detect AFP and hCG beta were labeled with europium (Eu) and samarium (Sm), respectively. Highly fluorescent chelates were developed by using the Delfia enhancement principle. The detection limits for AFP and hCG beta were approximately 0.02 kIU/L and approximately 0.2 IU/L, respectively. The within-run precision was &lt; 5% over the whole range of AFP (1-500 kIU/L) and hCG beta (1-200 IU/L) concentrations tested. Cross-reaction of intact hCG was &lt; 0.03%. The AFP concentrations determined with the dual-label assay correlated well with those obtained by Delfia AFP single-label kit. The concentrations of hCG beta were in good agreement with recently published data. Storing the serum samples for 24 h or 1 week at room temperature increased the hCG beta concentration by 4% and 26%, respectively. At 35 degrees C this dissociation of hCG increased 30-40-fold. Repeated freezing and thawing had no effect on the hCG beta concentration.