Cigarette smoking and serum lipid and lipoprotein concentrations: an analysis of published data

To examine the association between cigarette smoking in adults and serum lipid and lipoprotein concentrations the results of 54 published studies were analysed. Overall, smokers had significantly higher serum concentrations of cholesterol (3.0%), triglycerides (9.1%), very low density lipoprotein cholesterol (10.4%), and low density lipoprotein cholesterol (1.7%) and lower serum concentrations of high density lipoprotein cholesterol (-5.7%) and apolipoprotein AI (-4.2%) compared with nonsmokers. Among non-smokers and light, moderate, and heavy smokers a significant dose response effect was present for cholesterol (0, 1.8, 4.3, and 4.5% respectively), triglycerides (0, 10.7, 11.5, and 18.0%), very low density lipoprotein cholesterol (0, 7.2, 44.4, and 39.0%), low density lipoprotein cholesterol (0, -1.1, 1.4, and 11.0%), high density lipoprotein cholesterol (0, -4.6, -6.3, and -8.9%), and apolipoprotein AI (0, -3.7 and -5.7% in non-smokers and light and heavy smokers). These dose response effects may provide new evidence for a causal relation between exposure to cigarette smoke and changes in serum lipid and lipoprotein concentrations whether as a direct result of physiological changes or of dietary changes induced by smoking. Adequate prospective data to estimate the excess risk of coronary artery disease existed only for cholesterol concentration. When that information was combined with data from the present study, and given that smokers as a group face an average overall excess risk of coronary artery disease of 70%, it was estimated that the observed increased serum cholesterol concentration in smokers may account for at least 9% of that excess risk. Furthermore, the dose response effect of smoking on serum cholesterol concentration suggests a gradient of increased absolute risk of coronary artery disease between light and heavy smokers.

Reference distributions for the negative acute-phase serum proteins, albumin, transferrin and transthyretin: a practical, simple and clinically relevant approach in a large cohort

Inflammation is associated with diverse clinical conditions accompanied by characteristic changes in serum levels of the acute-phase proteins that can be used to stage the inflammatory process and evaluate the impact of treatment. Some acute-phase proteins increase during inflammation, while others, such as albumin, transferrin, and transthyretin, decrease. The current study reports reference ranges for serum levels of albumin, transferrin, and transthyretin based on a cohort of over 124,000 Caucasian individuals from northern New England, tested in our laboratory between 1986 and 1998. Measurements were standardized against CRM 470 (RPPHS) and analyzed using a previously validated statistical approach. Individuals with laboratory evidence of inflammation (C-reactive protein of 10 mg/L or higher) were excluded. The levels of all three analytes varied by age, generally rising until the second or third decade of life and then decreasing thereafter. Albumin and transthyretin levels were higher during midlife among males as compared to females; the maximum being at 25 years for albumin (5%) and 35 years for transthyretin (16%). In contrast, above the age of 10 years, transferrin levels were increasingly higher among females (7% at 20 years). When values were expressed as multiples of the age- and gender-specific median levels, the resulting distributions fitted a log-Gaussian distribution. When patient data are normalized in this manner, the distribution parameters can be used to assign a corresponding centile to an individual's measurement simplifying interpretation. The ultimate interpretation of an individual's measurement relies upon the clinical setting.

Apolipoproteins and ischaemic heart disease: implications for screening

Apolipoproteins and lipids are established risk factors of ischaemic heart disease (IHD) but their efficacy as screening tests is not known. We therefore examined the mortality from IHD and serum concentrations of lipids and apolipoproteins in a prospective study of 21,520 men aged 35-64 years. Serum apo B was the apolipoprotein most strongly associated with IHD risk; a decrease in apo B of 10% was associated with 22% lower risk of IHD. However, measurement of apo B alone detected only 17% of all IHD deaths at the cost of a 5% false-positive rate. Combining apo B with apo AI and apo (a) increased the detection rate to 19%. With systolic blood pressure, smoking, and family history of IHD the detection rate increased to 28%. We conclude that screening for IHD by measuring apo B alone or with apo AI and apo (a) is too poor to discriminate between recommending drug therapy or lifestyle change for some and not others. It is not advisable to screen for IHD by measuring any combination of cholesterol, apo B, apo AI, apo (a) and the other risk factors. The primary aim in prevention of ischaemic heart disease should be to lower the risk factors in the population.

Association between serum insulin growth factor-I (IGF-I) and a simple sequence repeat in IGF-I gene: implications for genetic studies of bone mineral density

We recently demonstrated that insulin growth factor-I (IGF-I) cosegregates with bone mineral density (BMD) in progenitor crosses of two inbred strains of mice. Additionally, we reported that men with idiopathic osteoporosis (IOM) have low serum IGF-I levels, which can be related to BMD and bone turnover. In this study, we considered the possibility that serum IGF-I levels are influenced by molecular genetic variation in the IGF-I structural gene, and that a polymorphic microsatellite (CA repeat) in this locus can be used as a genetic marker for such comparisons. We studied 171 men and women, classified according to the trial in which they were participating. First, in 25 Caucasian men with IOM we noted a very high frequency (64%) of homozygosity for the most common allele (192 bp) in a dinucleotide repeat 1 kb upstream from the transcription start site of the IGF-I gene. This compared with a frequency of only 32% in healthy populations (both men and women) (P < 0.004). Next, we determined that for 116 healthy Caucasian men and women the 192/192 genotype was associated with lower serum IGF-I levels than all other genotypes (192/192: 129 +/- 7 ng/mL vs. others: 154 +/- 7 ng/mL, P = 0.03). We also noted that subjects possessing one 194-bp allele exhibited serum IGF-I levels 25% higher than those homozygous for 192 bp (192/192), (P < 0.005) even after correction for age and sex. Similarly, for men with the 192/192 genotype, serum IGF-I concentrations were lower than any other genotype (145 +/- 10 ng/mL vs. 183 +/- 9 ng/ml P < 0.02). In conclusion, low serum IGF-I levels found in men with IOM are associated with homozygosity for a specific allele of the IGF-I microsatellite (192/192), and individual variation in serum IGF-I levels is influenced by genetic factors and may be specifically influenced by variation at the IGF-I structural locus. Further family and pedigree studies are needed to characterize the relationship of bone mass acquisition to the IGF-I genotype.

Lipoprotein(a) as a risk factor for ischemic heart disease: metaanalysis of prospective studies

Although in vitro studies support a pathophysiologic role for lipoprotein(a) [Lp(a)] in the development of atherosclerosis, and retrospective studies consistently report that there is a relationship between Lp(a) and ischemic heart disease (IHD), the conclusions drawn from prospective studies about this relationship have been inconsistent. To address this issue, we have performed a metaanalysis of data available from prospective studies. Lp(a) concentrations expressed as mass units vary markedly between studies, reflecting the need for assay standardization. In 12 of 14 prospective studies, Lp(a) concentrations are higher in subjects who later develop IHD (cases) than in those who do not (controls), although there is variation in the size of the effect. Sample storage temperature may contribute to this variability. When the studies are analyzed collectively, Lp(a) concentrations are significantly higher in cases than in controls, and the extent of the effect is similar in men and women. These findings provide evidence in support of a causal role for Lp(a) in the development of atherosclerosis. Measurement of Lp(a) may be useful to guide management of individuals with a family history of IHD or with existing disease. The separation in values between cases and controls is not, however, sufficient to allow the use of Lp(a) as a screening test in the general population.

Identifying Smith–Lemli–Opitz syndrome in conjunction with prenatal screening for Down syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is a rare hereditary disorder of cholesterol metabolism. We examine the feasibility of identifying SLOS as a part of a routine prenatal screening and evaluate diagnostic testing in maternal urine (or serum), in addition to amniotic fluid.

METHODS

Our SLOS risk algorithm utilized three Down syndrome screening markers (estimated 62% detection rate; 0.3% screen-positive rate). Fifteen North American prenatal screening programs implemented this algorithm.

RESULTS

SLOS risk was assigned to 1 079 301 pregnancies; 3083 were screen-positive (0.29%). Explanations were found for 1174, including 914 existing fetal deaths. Among the remaining pregnancies, 739 were screen-positive only for SLOS; 1170 were also screen-positive for other fetal disorders. Five of six SLOS pregnancies (83%) were screen-positive. All six had sonographic findings, were biochemically confirmed, and were terminated. Maternal urine steroid measurements were confirmatory in four cases tested. Second-trimester prevalence among Caucasians was 1 in 101 000 (1 in 130 000 overall; no cases in other racial groups). Among 739 pregnancies screen-positive only for SLOS, two cases were identified; another 69 had major fetal abnormalities.

CONCLUSIONS

Although SLOS occurred less often than previously reported, many other major abnormalities were detected. Implementing the algorithm as an adjunct to Down syndrome screening may be feasible.

Regulation of rat biliary cholesterol secretion by agents that alter intrahepatic cholesterol metabolism. Evidence for a distinct biliary precursor pool

Propensity for cholesterol gallstone formation is determined in part by biliary cholesterol content relative to bile salts and phospholipid. We examined the hypothesis that the rate of biliary cholesterol secretion can be controlled by availability of an hepatic metabolically active free cholesterol pool whose size is determined in part by rates of sterol synthesis, as reflected by activity of the primary rate-limiting enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and of sterol esterification, as reflected by the activity of the enzyme acyl coenzyme A/cholesterol acyltransferase (ACAT). Rats were prepared with biliary, venous, and duodenal catheters. The enterohepatic circulation of biliary lipids was maintained constant by infusion of a bile salt, lecithin, cholesterol replacement solution. Administration of 25-hydroxycholesterol decreased HMG CoA reductase activity, increased ACAT activity, and decreased biliary cholesterol output 26% by 1 h. By 2 h, ACAT activity and biliary cholesterol secretion were at control levels. Administration of mevinolin, a competitive inhibitor of HMG CoA reductase, had no effect on ACAT activity and decreased biliary cholesterol secretion 16%. Administration of progesterone, an inhibitor of ACAT, had no effect on HMG CoA reductase and increased biliary cholesterol output 32% at 1 h. By 2 h, all parameters were near control levels. None of these agents had any significant effect on biliary bile salt or phospholipid secretion. Thus, acutely altering rates of esterification and/or synthesis can have profound effects on biliary cholesterol secretion independent of the other biliary lipids. These experiments suggest the existence of a metabolically active pool of free cholesterol that serves as a precursor pool for biliary cholesterol secretion. Furthermore, the size of this precursor pool is determined in part both by rates of cholesterol synthesis and esterification and is a key determinant of biliary cholesterol secretion.

Genetic variation in lectin-like oxidized low-density lipoprotein receptor 1 (LOX1) gene and the risk of coronary artery disease

BACKGROUND

We examined the association of 3 polymorphisms in the lectin-like oxidized LDL receptor-1 (LOX1 or OLR1) gene with coronary artery disease in the Women's Ischemia Syndrome Evaluation (WISE) study population.

METHODS AND RESULTS

The WISE sample comprised 589 white and 122 black women who underwent angiography for suspected ischemia. The sample was divided into 3 groups: <20% stenosis (38.7%), 20% to 49% stenosis (24.9%), and >or=50% stenosis (35.3%). The three LOX1 polymorphisms (intron 4/G-->A, intron 5/T-->G, and 3' UTR/T-->C) were in linkage disequilibrium and thus behaved as a single polymorphism. The frequency of the 3'UTR/T allele was significantly higher in whites than blacks (49% versus 19%; P<0.0001). Among white women, the frequency of the 3'UTR/T allele carriers (TC+TT genotypes) increased gradually from 67.9% to 75.0% and 79.2% in the <20%, 20% to 49%, and >or=50% stenosis groups, respectively (chi2 trend=6.23; P=0.013). Logistic regression analyses indicated that APOE (odds ratio, 1.90; P=0.007) and LOX1 (odds ratio, 1.67; P=0.025) genotypes were independently associated with the risk of disease and that there was no interaction between the two genes. The 3'UTR/T allele carriers also had significantly higher IgG anti-oxLDL levels than individuals carrying the CC genotype (0.94+/-0.20 versus 0.86+/-0.16; P=0.032). Furthermore, our electrophoretic mobility shift assay data show that the 3'UTR polymorphic sequence affects the binding of a putative transcription factor in an allele-specific manner.

CONCLUSIONS

Our data suggest that common genetic variation in the LOX1 gene may be associated with the risk of coronary artery disease in white women.

Mid-gestational maternal free thyroxine concentration and offspring neurocognitive development at age two years

CONTEXT

Lower neurocognitive development scores at age 2 yr have been reported in association with euthyroid hypothyroxinemia during early pregnancy.

OBJECTIVE

The objective of this study was to further explore this association with euthyroid hypothyroxinemia during early pregnancy.

DESIGN

This was an observational, nested case-control study.

SETTING

The study was conducted at physician offices and prenatal clinics throughout Maine.

STUDY SUBJECTS

Between May 2004 and March 2006, TSH was measured in 5734 women in conjunction with second-trimester Down syndrome screening. After completion of pregnancy, free T(4) was measured in stored second-trimester sera from euthyroid women (TSH 0.1-3.5 mIU/ml; n = 5560). Women with free T(4) at the third centile or less (n = 99) were matched with women whose free T(4) was at the 10th to the 90th centile (n = 99).

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE

Bayley Scales of Infant Development (BSID III) were administered to the 198 offspring at age 2 yr. Scores for cognitive, language, and motor development were compared between matched pairs of offspring from the two groups before and after correcting for relevant variables.

RESULTS

Unadjusted BSID-III scores (cognitive, language, and motor) were lower by about 3% at age 2 yr among offspring of 98 hypothyroxinemic women (cases), reaching borderline significance for cognitive and motor scores. After adjustment for gestational age, the child's age at testing, maternal weight, and education, all differences diminished and became nonsignificant. Scores less than 85 were more frequent among case children but did not reach statistical significance (P = 0.14).

CONCLUSIONS

Isolated hypothyroxinemia during the second trimester is not associated with significantly lower BSID-III scores at age 2 yr, compared with scores for offspring of matched euthyroxinemic women.

Reference distributions for complement proteins C3 and C4: a practical, simple and clinically relevant approach in a large cohort

The two serum proteins of the complement cascade in the highest concentrations, C3 and C4, respond to various conditions in much the same manner as do other positive acute-phase proteins. A major difference is that they are relatively sluggish in response to cytokine drive, requiring several days rather than hours to be detectably elevated by serial measurements. As with other acute-phase proteins, there are many processes that up- or down-regulate synthesis, including infection or inflammation, hepatic failure, and immune-complex formation. Clinicians may find it difficult to distinguish among these processes, because they often occur simultaneously. The situation is further complicated by genetic polymorphism, with rare instances of markedly reduced synthesis and circulating levels, and consequent vulnerability to infection. C3 and C4 are measured for clinical purposes to help define certain rheumatic and immunologically mediated renal diseases. Interpreting the measured blood levels of these two components requires one to consider the intensity of the inflammatory drive, the timing of the suspected clinical process, the production of complement-consuming immune complexes, and the possible existence of benign circumstances. In this fifth article in a series, reference ranges for serum levels of two complement proteins (C3 and C4) are examined. The study is based on a cohort of over 55,000 Caucasian individuals from northern New England, who were tested in our laboratory in 1994-1999. Measurements were standardized against certified reference material (CRM) 470/reference preparation for proteins in human serum (RPPHS), and analyzed using a previously described statistical approach. Individuals with unequivocal laboratory evidence of inflammation (C-reactive protein of 10 mg/L or higher) were excluded. Our results show that the levels of C3 and C4 change little during life and between the sexes, except that they increase slightly and then fall after age 20 in males and at about age 45 in females. When values were expressed as multiples of the age- and gender-specific median levels, the resulting distributions fitted a log-Gaussian distribution well over a broad range. When patient data are normalized in this manner, the distribution parameters can be used to assign a centile corresponding to an individual's measurement, thus simplifying interpretation.

Assigning risk for Smith-Lemli-Opitz syndrome as part of 2nd trimester screening for Down's syndrome

OBJECTIVES

To design a reliable model in the context of prenatal screening for assigning the risk in an individual pregnancy of Smith-Lemli-Opitz syndrome (SLOS) and assess its performance.

SETTING

A 2nd trimester screening programme for Down's syndrome that measures unconjugated estriol (uE3) along with other serum markers.

METHODS

Development of individual risk estimates with a trivariate model incorporating measurements of maternal serum uE3, alpha-fetoprotein (AFP), and human chorionic gonadotropin (hCG) in both SLOS and unaffected pregnancies.

RESULTS

Population parameters were computed for the three analytes, as were pairwise correlation coefficients and truncation limits, based on an unbiased collection of 29 affected pregnancies. Published parameters were used for unaffected pregnancies. With a cut off level of risk of 1:50, 62% of SLOS pregnancies can be detected by initially identifying 0.34% of unaffected pregnancies as screen positive. About 1 in 90 screen positive pregnancies will be affected.

CONCLUSIONS

It is possible to screen for SLOS as an add on to existing 2nd trimester maternal serum screening, if uE3 is already being measured. A large, prospective trial is necessary to determine whether diagnostic testing can be performed in maternal urine or serum rather than amniotic fluid.

Reference distributions for immunoglobulins A, G, and M: a practical, simple, and clinically relevant approach in a large cohort

Serum immunoglobulins are measured millions of times each year, yet clinical interpretations remain hampered by inadequate age- and gender-specific reference limits. In order to provide more reliable and comprehensive reference distributions for IgA, IgG, and IgM measurements, we analyzed automated immunoassay values from 115,017 serum samples from northern New England patients (99% Caucasian) who were tested in our laboratory between 1986 and 1995. Measurements were standardized to reference material, CRM 470 (RPPHS). A simple, practical, and clinically relevant approach was used to determine reference distributions for the immunoglobulins over a wide range of ages for males and females. Levels of IgA and IgM varied considerably by age, and by gender for IgM. For each of the analytes, the observed 5th and 95th centiles were symmetric about the median and approximately constant over the entire age range. When immunoglobulin reference values are expressed as multiples of the age- and gender-specific regressed medians, the resulting distributions fit a log-Gaussian distribution well. This finding enables interpretation of serum immunoglobulin measurements using a common unit (multiples of the median) that is independent of age or gender. Insights gained from this study can help improve and simplify the interpretation of immunoglobulin measurements.

ELISA of IgG antibody to oxidized low-density lipoprotein: effects of blocking buffer and method of data expression

We describe an ELISA for serum IgG antibodies against malondialdehyde-modified low-density lipoprotein (mLDL). Optimal antigen concentration, serum dilution, and dilution of enzyme-conjugated second antibody were 25 mg/L, 1:250, and 1:5000, respectively, when 5 g/L human serum albumin was used for blocking. When data were expressed as mLDL/LDL (the ratio of IgG binding to mLDL vs LDL), within-run and between-run CVs were 7.0% and 8.9%, respectively. Antibody concentrations expressed as mLDL/LDL or as mLDL-LDL (the difference between IgG binding to mLDL and to LDL) were higher in women with systemic lupus erythematosus (n = 20) than in controls (n = 20) (P &lt; 0.001). With bovine serum albumin or Superblock blocking buffers, only the mLDL-LDL data were significant. Thus, the choice of blocking agent and the method of data expression should be carefully considered when assaying IgG antibodies against mLDL.

Effect of Sample Storage on the Assay of Lipoprotein(a) by Commercially Available Radial Immunodiffusion and Enzyme-Linked Immunosorbent Assay Kits

Lipoprotein(a) [Lp(a)] was measured by both a radial immunodiffusion (RID) kit from Immuno AG (Zurich, Switzerland) and a Tint Elize enzyme-linked immunosorbent assay (ELISA) kit from CytRx Biopool Ltd. (Umeå, Sweden) in serum samples that had been stored at -20 and -70 degrees C for six months. Storage temperature had no significant effect on the Lp(a) concentrations obtained by either method. After six months, mean Lp(a) degradation was 46% (95% confidence interval, 34-58%) with the RID kit; the ELISA data could not be compared between time points. In fresh sera, Lp(a) concentrations obtained by RID were 41% higher than by ELISA (because of differences in assay calibration materials), but in paired measurements of a set of 215 samples stored at -40 degrees C for an average of 10 years, Lp(a) concentrations were 62% lower by RID. This suggests that RID is more sensitive to the effects of long-term storage than is ELISA.

The relationship between apolipoprotein E and serum oxidation-related variables is apolipoprotein E phenotype dependent

To examine the relationship between apolipoprotein E and serum oxidation status, we assayed apolipoprotein E level, apolipoprotein E phenotype, and levels of lipid peroxides and transition metal ions and their binding proteins in sera from apparently healthy individuals. The study group included 129 women aged 22-63 years and 53 men aged 22-56 years. Among subjects with apolipoprotein E 4/3 phenotype, lipid peroxide levels were higher compared with E 3/2 phenotype (786 +/- 182 nmol/l vs. 659 +/- 174 nmol/l, P = 0.015), and ceruloplasmin levels were slightly higher compared with apolipoprotein E 3/3 phenotype (0.28 +/- 0.08 mg/l vs. 0.26 +/- 0.06 mg/l, P = 0.035). In the study group as a whole, there were significant associations between serum apolipoprotein E level, and serum levels of ceruloplasmin (r = 0.266, P < 0.001) and ferritin (r = 0.2, P < 0.007). Among subjects with apolipoprotein E 4/3 phenotype, there was a significant association between serum apolipoprotein E and lipid peroxide levels (r = 0.470, P < 0.01), which was not apparent among subjects with E 3/3 or E 3/2 phenotypes. In multivariate analysis, apolipoprotein E phenotype was a small but significant independent contributor to variation in serum lipid peroxide levels. These data suggest that there may be heterogeneity among apolipoprotein E phenotypes in their relationships with serum lipid oxidation status.

Dehydrosteroid measurements in maternal urine or serum for the prenatal diagnosis of Smith–Lemli–Opitz syndrome (SLOS)

In a large multi-center trial involving prenatal screening for Smith-Lemli-Opitz syndrome (SLOS), we evaluated maternal urine and serum steroid analysis as a non-invasive diagnostic alternative to amniotic fluid sterol analysis. Candidate steroid ratios included: 7-dehydropregnanetriol/pregnanetriol (7-PT/PT), 8-dehydropregnanetriol/PT (8-PT/PT), the sum of these two (7 + 8-PT/PT), and dehydroestriol/estriol (DHE3/E3). Results are presented from 19 SLOS pregnancies, and 732 reference pregnancies that were screen positive for SLOS but negative on testing in amniotic fluid. Steroid ratios are expressed as multiples of the 75th centile (MoS), rather than multiples of the median, as most reference measurements were undetectable. All four urine ratios were available in 12 SLOS pregnancies; the median 7-PT/PT MoS was 94, with no overlap between affected and reference pregnancies in the second trimester. The separation between these groups increased by 27% per week. The other three ratios performed similarly in urine, with (7 + 8)-PT/PT ratios being marginally superior, due to fewer high reference outliers. All four steroid ratios in urine were diagnostic for SLOS between 14 and 22 weeks' gestation. In six SLOS pregnancies in which all serum analytes were measured, the median 7-PT/PT MoS was 71, and there was slight overlap in the second trimester. The separation increased by 28% per week. Steroid ratios in serum were less definitive than in urine but might be useful in certain circumstances, at 14 weeks gestation or later. Urine testing performance prior to 14 weeks gestation appears promising, but reference data are sparse.

Reference distributions for serum iron and transferrin saturation: a practical, simple, and clinically relevant approach in a large cohort

The principal considerations driving iron status evaluation are clinical concern for anemia and the possibility of iron-storage disease. Most often, the circulating levels of transferrin (or total iron binding capacity) and serum iron are measured and the percentage of transferrin saturation (TSAT) is then computed. Optimally, reference ranges for these analytes should exclude the effects of the acute phase response, nutritional status, estrogen effect, specific genetic disorders, liver disease, and blood transfusion. The current study reports reference ranges for serum iron and TSAT within a cohort of over 55,000 Caucasians from northern New England, tested in our laboratory between 1994 and 1999. Measurements were standardized against serum reference material (SRM) 937 (for iron) and certified reference material (CRM) 470 (also called reference preparation for proteins in human serum (RPPHS)) (for transferrin), and analyzed using a previously published approach. Individual cases with evidence of inflammation (C-reactive protein > or =10 mg/L), or iron overload (TSAT >80% for males and >70% for females) or serum iron values <5 micro mol/L, were removed. Among the referent individuals, iron and TSAT levels rose slightly until the teen years, at which time levels in males increased while those in females remained essentially constant. Between 20 and 70 years of age, males had 10-15% higher iron levels and 15-20% higher TSAT levels than females. When values were expressed as multiples of the age- and gender-specific median levels, the serum iron and TSAT observations fit log-Gaussian distributions reasonably well from the 20th to 99th centile, and the 10th to the 99th centile, respectively. After normalization, the Gaussian parameters can be used to assign a corresponding centile to an individual's measurement, simplifying interpretation. These data provide new and more detailed reference ranges for serum iron and TSAT.

Implications of High Free Thyroxine (FT4) concentrations in euthyroid pregnancies: the FaSTER trial

CONTEXT

Lower birth weight has been reported in conjunction with high maternal free T4 (FT4) in euthyroid pregnancies, raising concerns for suboptimal outcomes.

OBJECTIVE

The objective of the study was to explore the relationships between high maternal FT4 and pregnancy complications in euthyroid women and to further examine the relationships among maternal size, FT4, and birth weight.

DESIGN

This was an observational multicenter cohort study.

SETTING

The study was conducted at prenatal clinics.

STUDY SUBJECTS

A total of 9209 euthyroid women with singleton pregnancies participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Relationships between second-trimester high maternal FT4 and pregnancy/delivery complications and, among FT4, maternal weight and birth weight were measured.

RESULTS

Women in the highest FT4 quintile are younger and weigh less than women in quintiles 1-4; gestational diabetes and preeclampsia occur less often (P = < .001, P < .001, P < .001, and P = .05, respectively). Lowest median birth weight occurs among women in the highest FT4 quintile (P = < .001), but deliveries less than 37 weeks' gestation are not increased. Labor/delivery complications do not differ by FT4 quintile. Restricting analyses to maternal weight-adjusted small-for-gestational-age deliveries yields similar results, except for preeclampsia. In the highest maternal weight decile, adjusted median birth weight is 266 g higher (8.3%) than in the lowest weight decile; adjusted median FT4 is 0.91 pmol/L lower (6.8%). Among women in the highest FT4 decile, adjusted median birth weight is 46 g lower (1.3%) than in the lowest FT4 decile. All three relationships are statistically significant (P < .001, P < .001, and P = .004, respectively).

CONCLUSIONS

Lower median birth weight among euthyroid women with high FT4 is not associated with adverse pregnancy outcomes. Further investigation is indicated to determine how the variations in thyroid hormone concentration influence birth weight.

The relationship between serum levels of lipoprotein(a) and proteins associated with the acute phase response

The association of serum lipoprotein(a) (Lp(a)) with inflammation was investigated in a primarily rheumatologic study group (n = 570; 202 males and 368 females) by studying the relationship between serum levels of Lp(a) and a panel of acute phase proteins (C-reactive protein (CRP), alpha 1-antitrypsin (AAT), alpha 1-acid glycoprotein (AGP), haptoglobin (HPT), complement components 3 and 4 (C3, C4), prealbumin (PAL), albumin (ALB) and transferrin (TRF)). Lp(a) data were adjusted for age and sex, but not clinical condition as no significant differences in Lp(a) levels were observed, using analysis of variance, among the 15 diagnostic categories in the study group. Univariate analyses revealed significant positive associations between Lp(a) levels and levels of C4, AGP, C3 and HPT. Multivariate analysis revealed that C4 and AGP (in descending order of significance) were significant independent predictors of Lp(a) concentration, together accounting for 2.9% of the variability in Lp(a) concentration in the present study group. The data indicate that confounding effects of an acute phase response should be considered in epidemiologic studies, if a high prevalence of inflammation is suspected.

Prevalence of steroid sulfatase deficiency in California according to race and ethnicity

OBJECTIVE

Estimate steroid sulfatase deficiency (STSD) prevalence among California's racial/ethnic groups using data from a previous study focused on prenatal detection of Smith-Lemli-Opitz syndrome (SLOS). SLOS and STSD both have low maternal serum unconjugated estriol (uE3) levels.

METHODS

Prevalence was estimated using three steps: listing clinically identified cases; modeling STSD frequency at three uE3 intervals using diagnostic urine steroid measurements; applying this model to determine frequency in pregnancies not providing urine.

RESULTS

Overall, 2151 of 777 088 pregnancies (0.28%) were screen positive; 1379 of these were explained and excluded. Fifty-four cases were diagnosed clinically among 707 remaining pregnancies with a male fetus. Urine steroid testing identified 74 additional STSD cases: 66 (89.2%) at uE3 values < 0.15 MoM, 8 (10.8%) at 0.15-0.20 MoM, and 0 (0%) at > 0.20 MoM. Modeling estimated 107.5 STSD cases among 370 pregnancies without urine samples. In males, STSD prevalence was highest among non-Hispanic Whites (1:1230) compared to Hispanics (1:1620) and Asians (1:1790), but differences were not significant. No STSD pregnancies were found among 65 screen positive Black women.

CONCLUSION

The overall prevalence estimate of 1:1500 males is consistent with published estimates and is reasonable for counseling, except among Black pregnancies where no reliable estimate could be made.

Background staining in immunoblot assays. Reduction of signal caused by cross-reactivity with blocking agents

Certain serum samples produce high background in Western and direct immunoblot assays that detect human serum IgG against specific antigens. We determined that this was due to a reaction between endogenous IgG and the membrane blocking agent (we refer to this as blocking-specific background). Using milk as blocking agent, we screened 107 sera by Western immunoblot or checkerboard immunoblot assays, and found that 6.5% of sera had background intensities sufficient to interfere with the interpretation of final results. Blocking-specific background was also observed using bovine serum albumin and other animal protein-based blocking agents. As the primary antibody in these immunoblot assays was human IgG, we investigated human serum albumin as a blocking agent; this approach eliminated the problem of blocking-specific background.

Oxidation-related analytes and lipid and lipoprotein concentrations in healthy subjects

The relations between oxidation-related analytes and lipoprotein risk factors for coronary heart disease are poorly understood. To address this issue, ceruloplasmin, copper, iron, ferritin, cotinine, lipid peroxides, cholesterol, triglyceride, apoB, apoA-I, and lipoprotein(a) levels were measured in sera from apparently healthy subjects (51 men and 115 women). Pairwise comparisons revealed strong positive associations (P < .001) of copper and ceruloplasmin with lipid peroxides, total cholesterol, triglycerides and apoB, of transferrin with apoA-I and cholesterol, and of ferritin with triglycerides. Serum levels of oxidation-related analytes did not differ between smokers and nonsmokers. In multivariate analysis, serum copper was the major independent determinant of serum lipid peroxide level, accounting for 15% of the variability in concentration (ferritin accounted for 1.6%). Copper and ceruloplasmin accounted for 20.5% of the variation in triglyceride levels; triglycerides and apoB accounted for 12% of the variability in ferritin levels; apoB and apoA-I accounted for 9% of the variability in transferrin levels. The data suggest that serum copper contributes to lipid peroxidation in vivo. There are significant associations between lipoprotein and transition metal-related analytes, and further work is needed to elucidate the physiological basis for these relations.

New laboratory guidelines for serologic diagnosis of Lyme disease: evaluation of the two-test protocol

Recent guidelines established by the Association of State and Territorial Public Health Laboratory Directors (ASTPHLD) and the U.S. Centers for Disease Control and Prevention (CDC) recommend the use of a two-test protocol for the serologic diagnosis of Lyme disease (LD). The two-test protocol relies on a sensitive screening test, which is followed by specific immunoglobulin M (IgM) and/or IgG immunoblotting (IB), depending on the date of disease onset, of all samples with equivocal and positive screening test results. We evaluated a commercially available IgM-IgG enzyme-linked immunosorbent assay (ELISA) and separate IB tests for IgM and IgG antibodies to Borrelia burgdorferi as candidate assays for the two-test protocol. Serum samples obtained from healthy controls (n = 29), from patients with diagnoses or laboratory findings associated with serologic cross-reactivity to LD (n = 24), and from patients with well-documented early- and late-stage LD provided by the CDC and the College of American Pathologists (n = 53) were examined to determine each assay's individual sensitivity and specificity. No false-positive results were detected among the healthy controls by either ELISA or IB, whereas four false-positive ELISA results were recorded within the cross-reactive group. None of these sera, however, were positive for either IgM or IgG reactivity according to IB band criteria. With regard to the patients with LD, we determined the sensitivity and specificity of the ELISA to be 96 and 100%, respectively, compared with the reference data provided for these specimens. When we compared our IB results with data from CDC, the assay sensitivity and specificity were 80 and 96.2%, respectively, for IgM and 81.8 and 95.8%, respectively, for IgG. Pursuant to this evaluation we assessed the suitability of the two-test protocol by performing a retrospective analysis using clinical history to define samples as positive or negative for LD. We determined clinical sensitivity and specificity for all study subjects (n = 112) to be 50 and 100%, respectively. A reduction in the clinical sensitivity of the two-test protocol was associated with a lack of antibody response or seroconversion in LD patients treated with antibiotics. We conclude that the CDC-ASTPHLD guidelines provide useful criteria for test performance and interpretation aimed at standardizing the serologic diagnosis of LD.