PURPOSE: In radioimmunoassay (RIA), the gamma counter is the important instrument for the accurate measurement. To manage quality assurance of RIA, the counting efficiency of gamma counter is one of the important parameters. The aimof this study was to evaluate the counting efficiency of gamma counters in multiple institutes on the base of traceability by using the certified reference materials (CRMs).METHODS: Twenty-three institutes that perform RIA were enrolled in this study. I-125 CRMs that were certified by National Institute of Standards and Technology (NIST) were used. Each institute was asked to count the activity of I-125 CRMs at most twice on all gamma counters in use. The counting efficiency of each well of counter was calculated on the base of NIST-certified information, corrected for I-125 decay for date of testing.RESULTS: From 23 institutes, 44 gamma counters were evaluated. The average counting efficiency of all wells was 85.9% and the standard deviation was 13.5%. As a mean value of each gamma counter, three gamma counters showed poor counting efficiency (less than 70%). The poorest counting efficiency was 7%. The counting efficiency of seven gamma counters was between 70 and 75%. Eight counters had the counting efficiency between 75 and 90%. More than half of counter (26 gamma counters) showed excellent counting efficiency (more than 90%). The standard deviation variation range of inter-well efficiency was from 0 to 11.2.CONCLUSION: The first survey on the counting efficiency of gamma counter was performed in South Korea. Most of the RIA laboratories have well managed the quality assurance of gamma counter.
Academies and Institutes ; Immunoradiometric Assay ; Korea ; Quality Control ; Radioimmunoassay

BACKGROUND/AIMS: Maternal thyroid dysfunction has been associated with adverse pregnancy outcomes. The purpose of our study was to establish trimester-specific reference intervals for thyroid hormones in pregnant women in Korea, where iodine intake is more than adequate and to examine pregnancy and perinatal outcomes in their offspring. METHODS: Among 459 healthy pregnant women who were screened, we enrolled 417 subjects who had negative results for thyroid autoantibodies. Serum thyroid stimulating hormone (TSH) and free thyroxine were measured using an immunoradiometric assay. Urine iodine concentration was measured using inductively coupled plasma-mass spectrometry in 275 women. Reference ranges of thyroid hormones were determined according to the guidelines of the National Academy of Clinical Biochemistry. Pregnancy and perinatal outcomes were compared according to maternal thyroid function. RESULTS: The reference ranges of serum TSH were 0.03 to 4.24 mIU/L in the first trimester, 0.13 to 4.84 mIU/L in the second trimester, and 0.30 to 5.57 mIU/L in the third trimester. Pregnancy and perinatal outcomes did not vary in mothers with subtle changes in thyroid function. CONCLUSIONS: Trimester-specific thyroid hormone reference intervals in Korean pregnant women differ from those of other countries with different iodine nutrition status and ethnicity. The establishment of population-based, reliable trimester-specific reference intervals is critical for the interpretation of thyroid function in pregnant women to avoid unnecessary tests and treatments.
Autoantibodies ; Biochemistry ; Female ; Humans ; Immunoradiometric Assay ; Iodine ; Korea* ; Mothers ; Nutritional Status ; Pregnancy Outcome ; Pregnancy Trimester, First ; Pregnancy Trimester, Second ; Pregnancy Trimester, Third ; Pregnancy* ; Pregnant Women ; Reference Values ; Republic of Korea ; Spectrum Analysis ; Thyroid Gland* ; Thyroid Hormones* ; Thyrotropin ; Thyroxine

Anemia, iron deficiency (ID), and iron deficiency anemia (IDA) are common disorders. This study was undertaken to determine the prevalence of anemia, ID, and IDA in Korean females. We examined the associations between IDA, heavy metals in blood, vitamin D level and nutritional intakes. The study was performed using on data collected from 10,169 women (aged > or =10 yr), including 1,232 with anemia, 2,030 with ID, and 690 with IDA during the fifth Korea National Health and Nutrition Examination Survey (KNHANES V; 2010-2012). Prevalence and 95% confidence intervals were calculated, and path analysis was performed to identify a multivariate regression model incorporating IDA, heavy metals in blood, vitamin D level, and nutritional intakes. The overall prevalence of anemia, ID and IDA was 12.4%, 23.11%, and 7.7%, respectively. ID and IDA were more prevalent among adolescents (aged 15-18 yr; 36.5% for ID; 10.7% for IDA) and women aged 19-49 yr (32.7% for ID; 11.3% for IDA). The proposed path model showed that IDA was associated with an elevated cadmium level after adjusting for age and body mass index (beta=0.46, P<0.001). Vitamin D levels were found to affect IDA negatively (beta=-0.002, P<0.001). This study shows that the prevalence of anemia, ID, and IDA are relatively high in late adolescents and women of reproductive age. Path analysis showed that depressed vitamin D levels increase the risk of IDA, and that IDA increases cadmium concentrations in blood. Our findings indicate that systematic health surveillance systems including educational campaigns and well-balanced nutrition are needed to control anemia, ID, and IDA.
Adolescent ; Adult ; Aged ; Anemia, Iron-Deficiency/*blood/*epidemiology ; Body Mass Index ; Cadmium/*blood ; Cross-Sectional Studies ; Female ; Humans ; Immunoradiometric Assay ; Middle Aged ; Nutrition Surveys ; Prevalence ; Regression Analysis ; Republic of Korea/epidemiology ; Risk ; Vitamin D/*blood ; Young Adult

BACKGROUND: Measurement of postoperative serum thyroglobulin (Tg) is important for detecting persistent or recurrent differentiated thyroid cancer. We evaluated the analytic performance of the DxI 800 assay (Beckman Coulter, USA) for serum Tg and anti-thyroglobulin antibodies (TgAbs) in comparison with that of the GAMMA-10 assay (Shinjin Medics Inc., Korea) for serum Tg and RIA-MAT 280 assay (Stratec, Germany) for TgAb. METHODS: We prospectively collected blood samples from 99 patients thyroidectomized for thyroid cancer. The functional sensitivity was investigated in standards and human serum. Precision and linearity were evaluated according to the guidelines of the Clinical and Laboratory Standards Institute. The correlation between the two assays was assessed in samples with different Tg ranges. RESULTS: The functional sensitivity of the DxI 800 assay for serum Tg was between 0.0313 and 0.0625 ng/mL. The total CV was 3.9-5.6% for serum Tg and 5.3-6.9% for serum TgAb. The coefficient of determination (R2) was 1.0 and 0.99 for serum Tg and TgAb, respectively. The cut-offs for serum TgAb were 4.0 IU/mL (DxI 800) and 60.0 IU/mL (RIA-MAT 280), and the overall agreement was 68.7%. The correlation between the two assays was excellent; the correlation coefficient was 0.99 and 0.88 for serum Tg and TgAb, respectively. CONCLUSIONS: The DxI 800 is a sensitive assay for serum Tg and TgAb, and the results correlated well with those from the immunoradiometric assays (IRMA). This assay has several advantages over the IRMA and could be considered an alternative test for Tg measurement.
Autoantibodies/*blood ; Humans ; Immunoradiometric Assay ; Luminescent Measurements ; Prospective Studies ; Reagent Kits, Diagnostic ; Reproducibility of Results ; Thyroglobulin/*blood ; Thyroid Neoplasms/*diagnosis/surgery

BACKGROUND/AIMS: Quantification of hepatitis B surface antigen (HBsAg) is an emerging serologic test and may be useful for identifying treatment strategies for chronic hepatitis B (CHB). This study aimed to evaluate HBsAg titers during the natural course of CHB and identify correlations between HBsAg titers and hepatitis B virus (HBV) DNA concentrations across different CHB phases measured using an immunoradiometric assay (IRMA). METHODS: CHB phases were defined on the basis of HBV DNA concentrations, the presence of hepatitis B e antigen/antibody (HBeAg/Ab) and serum alanine aminotransferase levels. Serum HBsAg titers and paired HBV DNA concentrations in the different phases of CHB were compared using 627 serum samples. RESULTS: Mean HBsAg titers were significantly higher in the immunotolerant (IT) phase and immunoreactive (IR) HBeAg-positive phase than in the low-replicative (LR) and HBeAg-negative CHB (ENH) states. The correlation between HBsAg titers and HBV DNA concentrations was modest in the IT (n=36, r=0.804, p<0.001) and IR (n=48, r=0.773, p<0.001) phases, and it was poor in the LR state (n=116, r=0.289, p=0.002); however, no significant correlation was observed in the ENH state (n=67, r=0.146, p=0.237) or in the oral nucleos(t)ide analogue-treated group (n=267). CONCLUSIONS: HBsAg quantification using IRMA might be useful for discriminating different CHB phases and different stages of chronic liver disease.
Adult ; Alanine Transaminase/blood ; Biomarkers/blood ; DNA, Viral/*blood ; Disease Progression ; Female ; Hepatitis B Surface Antigens/*blood ; Hepatitis B e Antigens/blood ; Hepatitis B virus/*genetics/immunology ; Hepatitis B, Chronic/*immunology ; Humans ; *Immunoradiometric Assay ; Male ; Middle Aged ; Seoul ; Viral Load ; Virus Replication

BACKGROUND: Serum insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels are known markers of growth hormone (GH) secretion. The clinical utility of serum IGF-I and IGFBP-3 testing, however, remains controversial. The aims of this study were to evaluate the usefulness of IGF-I and IGFBP-3 as indicators of GH secretion through the GH stimulation test and to investigate whether a decrease in serum IGF-I levels in children with short stature, regardless of the cause, can be used as a screening test for short stature. METHODS: A total of 262 children presented with short stature, precocious puberty, or premature thelarche and were grouped into 7 tiers based on the 2007 growth chart. Serum IGF-I and IGFBP-3 levels and GH stimulation were analyzed using an immunoradiometric assay, and the data from 68 children who were below the 3rd percentile for height were used to evaluate the usefulness of IGF-I and IGFBP-3 as markers of GH status. RESULTS: GH deficiency was confirmed by the GH stimulation test in 25 of the 68 children, and 15 (15/25, 60%) and 4 (4/25, 16%) of them showed a decrease in IGF-I and IGFBP-3 levels, respectively. The sensitivity and specificity for predicting GH secretion were 60% and 16%, respectively, for IGF-1 and 41.9% and 97.7%, respectively, for IGFBP-3. Decreased serum IGF-I levels were more frequently observed in children below the 25th percentile than in those in the 25th to 95th percentiles. CONCLUSIONS: IGF-I and IGFBP-3 levels have been used as a screening tool for GH secretion in children with short stature, but based on the results of the GH stimulation test in the current study, the levels of IGF-I and IGFBP-3 might not be useful as markers of GH secretion. Evaluating serum IGF-I levels alone is not a sufficient screening test for children with a short stature.
Child* ; Growth Charts ; Growth Hormone ; Humans ; Immunoradiometric Assay ; Insulin-Like Growth Factor Binding Protein 3* ; Insulin-Like Growth Factor I* ; Mass Screening ; Puberty, Precocious ; Sensitivity and Specificity

PURPOSE: The effectiveness of gonadotropin releasing hormone (GnRH) agonist therapy in central precocious puberty (CPP) depends on the suppression of luteinizing hormone (LH) secretion. The purpose of this study was to determine the utility of a single luteinizing hormone measurement after GnRH agonist injection for the therapeutic monitoring of CPP. METHODS: The study included 148 females with CPP who had been treated with GnRH agonist. During the therapy, suppression of their pubertal development was assessed based on their height standard deviation score (SDS), bone age, and pubertal stage. Every six months, their serum LH and follicular stimulating hormone (FSH) levels were measured using immunoradiometric assays. Their estradiol levels were also assayed using radioimmunoassay two hours following GnRH agonist administration. RESULTS: The means of the onset age, bone age, and chronological age were 7.2 +/- 0.93, 10.1 +/- 1.1, and 8.2 +/- 0.94 years, respectively. Eight patients had pathologic intracranial lesions including harmatoma, hydrocephalus, meningitis, astrocytoma, and Rathke's cleft cyst. The basal and peak LH levels were 1.56 +/- 1.1 and 18.2 +/- 12.1 IU/L, respectively. In 39 females with CPP, pubertal development was not sufficiently suppressed even after one year of therapy. The receiver operating characteristic (ROC) curve showed a cutoff value of LH for pubertal suppression of less than 2.5 IU/L. The area under the curve (AUC) was 0.674. CONCLUSION: The cutoff value of 2.5 IU/L for a LH measurement, taken two hours following subcutaneous GnRH agonist injection, is adequate for therapeutic monitoring of females with CPP. This method is both convenient and cost effective.
Age of Onset ; Astrocytoma ; Estradiol ; Female ; Gonadotropin-Releasing Hormone ; Humans ; Hydrocephalus ; Immunoradiometric Assay ; Lutein ; Luteinizing Hormone ; Meningitis ; Piperazines ; Puberty, Precocious ; Radioimmunoassay ; ROC Curve

PURPOSE: The effectiveness of gonadotropin releasing hormone (GnRH) agonist therapy in central precocious puberty (CPP) depends on the suppression of luteinizing hormone (LH) secretion. The purpose of this study was to determine the utility of a single luteinizing hormone measurement after GnRH agonist injection for the therapeutic monitoring of CPP. METHODS: The study included 148 females with CPP who had been treated with GnRH agonist. During the therapy, suppression of their pubertal development was assessed based on their height standard deviation score (SDS), bone age, and pubertal stage. Every six months, their serum LH and follicular stimulating hormone (FSH) levels were measured using immunoradiometric assays. Their estradiol levels were also assayed using radioimmunoassay two hours following GnRH agonist administration. RESULTS: The means of the onset age, bone age, and chronological age were 7.2 +/- 0.93, 10.1 +/- 1.1, and 8.2 +/- 0.94 years, respectively. Eight patients had pathologic intracranial lesions including harmatoma, hydrocephalus, meningitis, astrocytoma, and Rathke's cleft cyst. The basal and peak LH levels were 1.56 +/- 1.1 and 18.2 +/- 12.1 IU/L, respectively. In 39 females with CPP, pubertal development was not sufficiently suppressed even after one year of therapy. The receiver operating characteristic (ROC) curve showed a cutoff value of LH for pubertal suppression of less than 2.5 IU/L. The area under the curve (AUC) was 0.674. CONCLUSION: The cutoff value of 2.5 IU/L for a LH measurement, taken two hours following subcutaneous GnRH agonist injection, is adequate for therapeutic monitoring of females with CPP. This method is both convenient and cost effective.
Age of Onset ; Astrocytoma ; Estradiol ; Female ; Gonadotropin-Releasing Hormone ; Humans ; Hydrocephalus ; Immunoradiometric Assay ; Lutein ; Luteinizing Hormone ; Meningitis ; Piperazines ; Puberty, Precocious ; Radioimmunoassay ; ROC Curve

Insulin-like growth factor system (IGF system) has been reported to be associated with the variety of disorders of myocardial function. However, the effect of myocardial infarction (MI) on the IGF system has not been fully described. Thus, the present study was to investigate in more detail the changes of IGF system in the male rat following myocardial infarction (MI). Ligation of the left coronary artery was performed in male Sprague-Dawley male rats at 60 days of age. Control rats were obtained sham-operated animals. MI rats were sacrificed at 1, 3, 7, 14, and 30 day after ligation of left anterior descending coronary artery. Control rats were sacrificed on 30 day after thoracotomy. Myocardial infarct size was assessed by planimetry and perimetry. Serum and heart concentrations of IGF-I and -II were determined by radioimmunoassay. Serum levels of IGF-binding protein (IGFBP)-1 and IGFBP-3 were analyzed with a two-site immunoradiometric assay. Mean infarct size was 35.2~42.3% of the left ventricle after coronary occlusion in experimental groups. Serum levels of IGF-I were markedly reduced, but the levels of IGF-II were not altered in MI rats compared with shamligated controls. Serum IGFBP-I levels in MI rats were significantly increased at 1 and 3 day compared with sham rats. The levels of serum IGFBP-3 were significantly higher in the ligated rats. IGF-I levels of the infarct/periinfarct area of the left ventricle were significantly decreased in rats with myocardial infarction, whereas the levels of IGF-II remained unchanged. These results demonstrate that the IGF system is altered in the myocardial infarction and suggest that the IGF system plays an important role in the response of the heart to myocardial infarction.
Animals ; Coronary Occlusion ; Coronary Vessels ; Heart ; Heart Ventricles ; Humans ; Immunoradiometric Assay ; Insulin-Like Growth Factor Binding Protein 3 ; Insulin-Like Growth Factor I ; Insulin-Like Growth Factor II ; Ligation ; Male ; Myocardial Infarction ; Radioimmunoassay ; Rats ; Salicylamides ; Thoracotomy ; Visual Field Tests

OBJECTIVE: Umbilical leptin concentrations have been associated with whole-body mineral content, fetal bone growth stimulation, pulmonary development in utero, nutritional intake, energy metabolism, and adiposity in children and adults. In this study, we investigated the effect of maternal factor, placental factor and fetal factor on cord blood leptin concentrations. METHODS: We measured leptin concentration in umbilical cord blood using immunoradiometric assay in 50 women with uncomplicated singleton term pregnancies. we analyzed the correlation of leptin level with maternal age, sex, gestational age, smoking, placental weight, neonatal body mass index, maternal body mass index, head circumference, and chest circumference by simple linear regression. RESULTS: There were significant correlation between leptin and gestational age, fetal BMI, head circumference, and chest circumference with correlation coefficient 0.244 (P=0.010), 0.182 (P=0.030), 0.243 (P=0.011), and 0.228 (P=0.014), respectively in the male neonates. There were significant correlation between leptin and fetal BMI with correlation coefficient 0.341 (P=0.003) in the female neonates. No statistically significant correlation between the concentration of leptin and neonatal gender was observed, in spite of higher mean value of female leptin concentration level. Also no statistically significant correlation between the concentration of leptin and smoking and drinking of mother was observed. CONCLUSION: In this study, leptin is significantly correlated with maternal age, maternal BMI, gestational age, fetal BMI, and chest circumference. It was suggested that leptin level was more associated with maternal factor and fetal factor than placental factor.
Adiposity ; Adult ; Body Mass Index ; Bone Development ; Child ; Drinking ; Energy Metabolism ; Female ; Fetal Blood ; Gestational Age ; Head ; Humans ; Immunoradiometric Assay ; Infant, Newborn ; Leptin ; Male ; Maternal Age ; Mothers ; Pregnancy ; Smoke ; Smoking ; Thorax ; Umbilical Cord