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Biochemical epidemiology: uses in the study of human carcinogenesis.

The use of biochemical markers may improve the potentialities of etiologic epidemiology. Exposure markers or markers of biologically effective dose allow better exposure assessment, therefore decreasing misclassification in epidemiological studies. Markers of individual susceptibility (such as metabolic polymorphism) permit the identification of subgroups of subjects at higher risk of cancer. In general, the integration of biochemical methods and an epidemiological design is helpful in the study of the sources of interindividual variability in response to carcinogenic stimuli. We review several investigations making use of biochemical measurements in the field of cigarette-induced bladder cancer.

Biomarkers↗

Requirements for improving quality in the measurement of bone markers.

BACKGROUND: A number of biochemical assays readily detect molecules released from the bone matrix and collagen degradation in both serum and urine specimens. The variability of bone biochemical markers is still an issue of practical concern limiting their wider clinical use, and compromising the management of the individual patient. The aim of the present study was to define quality specifications of bone markers measurement in the total testing process. METHODS: The different sources of biological variability of biochemical bone marker were assessed according to the current knowledge and categorized as pre-analytical, intra-analytical and post-analytical. RESULTS: The identification of factors influencing bone marker measurements allowed recommendations to be made for decreasing pre- and intra-analytical variation in order to improve laboratory performance. The assessment of post-analytical sources of variation, moreover, involves the practical use of bone markers in identifying individual women at risk of fractures and the identification of non-responders, providing adequate limit value, least significant change value or optimal threshold of bone marker change. CONCLUSIONS: Laboratory services may improve the potential clinical applications of biochemical markers of bone remodeling by improving method standardization, defining and reducing pre-analytical and analytical variables and providing reports that specify analytical and biological variation or cut-off values, thus facilitating data interpretation or reports.

Analysis of Variance↗

The rate at which serum total beta-subunit human chorionic gonadotropin increases after embryo transfer is a predictor of the viability of pregnancy and an identifier of determinants of pregnancy.

OBJECTIVE: To determine whether elements of treatment associated with faster doubling times of total beta-hCG in serum (beta-t2) in pregnant patients are also associated with a higher likelihood of pregnancy in all patients. DESIGN: Retrospective analysis of beta-t2 values, elements of ovarian stimulation (COH), and outcomes. SETTING: Private assisted reproductive technology (ART) center. PATIENT(S): Initial analysis of data from 432 cycles in which conception occurred after COH and embryo transfer, followed by analysis of pregnancy outcomes after 1,287 cycles of COH/ embryo transfer. INTERVENTION(S): No interventions. MAIN OUTCOME MEASURES: The beta-t2 values initially computed from consecutive serum beta-hCG levels in ongoing pregnancies were correlated with multiple properties of the patients and their treatment cycles. RESULT(S): The beta-t2 values during early pregnancy increased exponentially from about 1.6 days at 12 days to about 3.0 days at 24 days after embryo transfer. In those pregnancies which spontaneously aborted, early average beta-t2 values were higher than those for ongoing pregnancies; absolute beta-hCG levels did not differ. Positive correlations were established between beta-t2 values, the number of days of stimulation, and the number of ampules of drug administered per oocyte retrieved. The beta-t2 values were inversely related to average numbers of blastomeres in transferred embryos. Ongoing pregnancy rates (PR) were higher for cycles with lower gonadotropin dosages per oocyte retrieved, and when the average number of blastomeres in transferred embryos was higher. CONCLUSION(S): Steeper beta-hCG doubling times in early pregnancy were associated with lower gonadotropin dosages during ovarian stimulation and with higher numbers of blastomeres in transferred embryos. The latter variables were, in turn, associated with a higher likelihood of pregnancy after embryo transfer.

Adult↗

Detergents with different chemical properties induce variable degree of cytotoxicity and mRNA expression of lipid-metabolizing enzymes and differentiation markers in cultured keratinocytes.

The knowledge how detergents with different chemical properties influence epidermal keratinocytes is sparse. In the present study, the effects of five detergents were examined with respect to cell-toxicity and mRNA expression of key-enzymes in barrier lipid production and keratinocyte differentiation markers. First, the LD(50) for each detergent were determined. Secondly, keratinocytes were exposed to sub-toxic concentrations and the mRNA expression was analysed by real-time PCR after 24 h exposure to the detergents. SLS and CAPB induced a concentration-dependent increase in the expression of enzymes producing cholesterol and ceramides, while transcripts of enzymes producing fatty acids were unaffected. SLES and cocoglucoside increased the expression of certain enzymes involved in cholesterol and fatty acid synthesis while sodium cocoamphoacetate (SCAA) stimulated expression of transcripts involved in fatty acid synthesis. The expression of differentiation markers were increased by SLS, SLES and CAPB, while SCAA and cocoglucoside exhibited no effect. The present findings show that detergents have variable effects on lipid synthesis and keratinocyte differentiation, which could partly explain their barrier destruction potential in vivo.

Azo Compounds↗

Changes in immune activation markers during pregnancy and postpartum.

Changes in CD4 + cell levels and other immune parameters have been reported to occur during pregnancy but the timing of these alterations and their relationship to changes in immune function have not been well characterized. In addition, the influence of sociodemographic, obstetric, and other covariates on these relationships is largely unknown. We measured three immune activation markers, soluble interleukin-2 receptor (sIL-2Ralpha), soluble CD8 antigen (sCD8), and neopterin during pregnancy and postpartum in 170 HIV-1-seronegative women enrolled in the Mothers and Infants Cohort Study. Ante-partum and postpartum changes in these markers were examined using multivariable longitudinal random effects models. Neopterin levels began to rise well before delivery and were in decline by 2 months postpartum. sIL-2Ralpha and sCD8 levels increased at or near delivery and peaked by 2 months postpartum. After adjustment for other variables, the peak in sIL-2Ralpha was greater among women with pre-term than full-term deliveries (P = 0.05). All three markers were higher in whites than non-whites and in 'hard' drug users than non-users (P < or = 0.001 for each). After adjustment for these and other variables, hepatitis C virus (HCV) seropositivity was associated with higher levels of sCD8 and neopterin (P < or = 0.001 for each) but not sIL-2Ralpha (P = 0.27). These longitudinal data indicate that a state of broad immune activation develops at or near delivery. A number of maternal variables appear to influence the magnitude of these changes.

Adult↗

Nuchal translucence incorporated into a one-stage multifactorial screening model for Down syndrome prediction at second-trimester pregnancy.

The aim of this study was to achieve one-stage screening for trisomy 21 using a combination of nuchal translucency (NuT) measurement and maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (hCG) biochemistry levels in the second trimester among a high-risk study population. From January 1998 to June 2001, 45 cases of trisomy 21 were prenatally found and confirmed in the hospital-based cytogenetic diagnosis laboratory. A total of 867 normal singleton pregnancies were enrolled as controls from the antenatal care clinics in the hospital. All study and control subjects between 13 weeks and 18 weeks of gestation with a mean age of 15.2 +/- 1.3 weeks underwent one-stage nuchal translucence measurements and maternal serum biochemical screening for Down syndrome. The final logistic model contained beta-hCG (multiples of the gestational median or MoM), maternal age (matA), nuchal translucence (NuT MoM) and AFP (MoM) as covariates. Also, the estimated coefficients of the regression were highly significant. This model provided the estimated probability of Down syndrome as follows: Pr (Down syndrome) = exp (Z)/ [1 + exp (Z)], where Z = -11.18 + 0.64 x (beta-hCG MoM) + 0.25 x matA + 1.32 x NuT MoM -2.23 x AFP MoM. The logistic regression with estimated coefficients was installed in a Palm digital assistant (PDA) equipped with Excel (Microsoft). The risk probability of Down syndrome could be readily calculated after inputting data for all four predictor variables.

Adult↗

Mac-2 binding protein is a cell-adhesive protein of the extracellular matrix which self-assembles into ring-like structures and binds beta1 integrins, collagens and fibronectin.

Human Mac-2 binding protein (M2BP) was prepared in recombinant form from the culture medium of 293 kidney cells and consisted of a 92 kDa subunit. The protein was obtained in a native state as indicated by CD spectroscopy, demonstrating alpha-helical and beta-type structure, and by protease resistance and immunological analysis. It was highly modified by N- and O-glycosylation but not by glycosaminoglycans. Ultracentrifugation showed non-covalent association into oligomers with molar masses of 1000-1500 kDa. Electron microscopy showed ring-like shapes with diameters of 30-40 nm. M2BP bound in solid-phase assays to collagens IV, V and VI, fibronectin and nidogen, but not to fibrillar collagens I and III or other basement membrane proteins. The protein also mediated adhesion of cell lines at comparable strength with laminin. Adhesion to M2BP was inhibited by antibodies to integrin beta1 subunits but not to alpha2 and alpha6 subunits, RGD peptide or lactose. This distinguishes cell adhesion of M2BP from that of laminin and excludes involvement of lactose-binding galectin-3. Immunological assays demonstrated variable secretion by cultured human cells of M2BP, which was detected in the extracellular matrix of several mouse tissues.

Animals↗

Constitutional, biochemical and lifestyle correlates of fibrinogen and factor VII activity in Polish urban and rural populations.

BACKGROUND: Fibrinogen and factor VII activity are known to be related to atherosclerosis and coronary heart disease, but population differences in clotting factors and modifiable characteristics that influence their levels have not been widely explored. METHODS: This paper examines correlates of plasma fibrinogen concentration and factor VII activity in 2443 men and women aged 35-64 in random samples selected from the residents in two districts in urban Warsaw (618 men and 651 women) and from rural Tarnobrzeg Province (556 men and 618 women) screened in 1987-1988, and assesses which characteristics might explain urban-rural differences. Fibrinogen and factor VII activity were determined using coagulation methods. RESULTS: Fibrinogen was 12.9 mg/dl higher in men and 14.1 mg/dl higher in women in Tarnobrzeg compared to Warsaw. Factor VII activity was higher in Warsaw (9.2% in men and 15.3% in women). After adjustment for selected characteristics, fibrinogen was higher in smokers compared to non-smokers by 28 mg/dl in men and 22 mg/dl in women. In women, a 15 mg/dl increase in HDL-cholesterol was associated with a 10 mg/dl decrease in fibrinogen (P < 0.01). After adjustment for other variables, a higher factor VII activity in Warsaw remained significant (a difference of 9.4% in men and 14.8% in women). Lower fibrinogen in Warsaw remained significant only in women (15.4 mg/dl difference). CONCLUSIONS: The study confirmed that sex, age, BMI, smoking and blood lipids are related to clotting factors. However, with the exception of gender differences and smoking, associations between clotting factors and other variables were small and of questionable practical importance.

Adult↗

Early detection and intervention in schizophrenia: research.

The data supporting early detection and intervention are preliminary but suggestive enough to warrant further research. Overall, we need to focus greater attention on the early course of schizophrenia, including defining and describing early course, detecting cases early at onset or in the prodrome, testing whether early detection and treatment enhances treatment response and prognosis, and predicting at-risk cases early in the prodromal phase. Designs to address these questions are presented, and relevant issues are discussed, including study aims and hypotheses, definitions and measures of early phases and caseness, detection (and early detection), treatment interventions, dependent and independent variables, and ethical issues. The technical challenges of this research are substantial, but the potential gains for our understanding of schizophrenia and treatment make the effort compelling.

Biomarkers↗

Achalasia of the cardia in Allgrove's (triple A) syndrome: histopathologic study of 10 cases.

Allgrove's syndrome, i.e., achalasia, addisonianism, alacrima (OMIM 231550) is an autosomal recessive disorder recently associated with the AAAS gene coding for the Aladin protein. However, the pathophysiology of achalasia in Allgrove's syndrome remains obscure. Here we investigated the histopathology of the cardia in Allgrove's syndrome. Myectomy specimens from 10 children with Allgrove's syndrome and four normal cardia were studied by routine staining and by immunohistochemistry for the pan-neuronal marker PGP9.5, neuronal NO synthase, interstitial cells of Cajal, and CD3+ lymphocytes. In the normal cardia, myenteric ganglia, intramuscular nerve fibers, and interstitial cells of Cajal were numerous, whereas myenteric fibrosis and lymphocyte infiltrates were absent. In Allgrove's syndrome, fibrosis of the intermuscular plane was prevalent in all patients. Myenteric ganglia were absent, decreased, or apparently normal in 1 of 10, 8 of 10, and 1 of 10, respectively. Neuronal NO synthase was absent in 7 of 10 and decreased in 3 of 10, whereas interstitial cells of Cajal appeared normal in 7 of 10 and decreased in 3 of 10. Lymphocytes infiltrating the myenteric plexus were present in 6 of 10. Pyloromyectomy specimens available for six patients showed normal histopathologic features. In conclusion, the lack of neuronal NO synthase and fibrosis of the intermuscular plane can be linked to the defective cardia relaxation. Other features were less constant and may reflect the variability of disease expression and progression among patients with Allgrove's syndrome.

Adolescent↗

Increased bone resorption in the proximal femur in patients with hemiplegia.

OBJECTIVES: To investigate the relationship between the proximal femoral bone mineral density and bone resorption markers, determinants of calcium metabolism and vitamin D levels in elderly stroke patients. DESIGN: A total of 80 patients and 20 controls were enrolled in the study. Bone mineral density measurements were obtained at the proximal femur. In all subjects, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, intact parathyroid hormone, osteocalcin, deoxypyridinoline, and ionized calcium concentrations were measured. Barthel Index and Motricity Index Leg Score were recorded all patients. RESULTS: The serum concentrations of deoxypyridinoline, intact parathyroid hormone, and the mean serum ionized calcium levels were significantly higher in patients with stroke than that of the control subjects. The mean serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations in patients were significantly lower than those of the control group (P < 0.05). The bone mineral density of proximal femurs of paretic limbs was decreased significantly compared with those of the control group (P < 0.05). There were significant correlations between the Z score of the hemiplegic side and the patients' Barthel Index, Motricity Index Leg Score, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, calcium, and deoxypyridinoline. CONCLUSIONS: This study provides clear evidence that decreased mobility, vitamin D status, and bone turnover variables in patients after stroke are important factors in the greater bone loss in the paretic leg.

Aged↗

Biochemical markers of myocyte injury in heart failure.

This review discusses the role of biochemical markers of myocyte injury in patients with chronic congestive heart failure. Heart specific assays have been developed for the measurement of cardiac troponin T (cTnT), cardiac troponin I (cTnI), heart type fatty acid binding protein (H-FABP), and myosin light chain 1 (MLC-1). Concentrations of these biochemical markers increase in the absence of ischaemic events in the subset of patients with heart failure whose long term outcomes are most adverse. The markers are easy to measure serially and it is therefore easy to follow patients without inter-observer variability. The serial clinical use of these markers, separately or in combination, will sharpen our understanding of the state of heart failure.

Biomarkers↗

Variability of tumor markers in the follow-up of patients radically resected for breast cancer.

The biological and analytical components of variability of tumor markers should be distinguished from the variations due to tumor progression. The aim of the present study was to evaluate tumor marker variability in the follow-up of patients resected for breast cancer. So far, we have carried out 2,085 CEA and 2,550 CA 15-3 determinations in 435 patients. The total variability of both CEA and CA 15-3 was widely scattered among different subjects (CEA coefficient of variation 0-105%; CA 15-3 coefficient of variation 0-89.2%). The biological variability of CA 15-3, which was calculated in a limited number of cases, was scattered between 0 and 23% and was higher than the intra-assay variability. From these findings we conclude that when evaluating serial marker assays the intra-individual variability should be assayed initially to obtain a reference value of individual variability in relapse-free conditions.

Analysis of Variance↗

Serum dehydroepiandrosterone sulfate levels as an individual marker.

To assess the significance of the serum dehydroepiandrosterone sulfate (DHEAS) concentration as a parameter of the individual hormonal milieu, two different groups of subjects were studied: DHEAS levels were determined 3 times at 6-month intervals in 47 elderly hospitalized women, aged 71-94 yr (group 1), and 6 times over 2 consecutive weeks in 10 healthy male volunteers, aged 24-30 yr (group 2). For reference, serum cortisol (F) levels were determined concomitantly. In each group and on each sampling occasion, the subjects were ranked according to their DHEAS or F values. The stability over time of the ranking was much higher for DHEAS than for F; estimated concordance coefficients were 92% (group 1) and 88% (group 2) for DHEAS vs. 51% (group 1) and 49% (group 2) for F. We conclude that due to a comparatively low within- to between-subject variability ratio, DHEAS is a highly specific individual marker.

Adult↗

Monitoring alendronate therapy for osteoporosis.

Alendronate is an antiresorptive therapy for osteoporosis and results in a decrease in bone turnover. To choose the optimal measurement for monitoring this therapy, the size of the change needs to be compared with the variability of the measurement. We studied 26 women with postmenopausal osteoporosis (bone mineral density [BMD] T score < -2.5), who were randomized in a 2:1 ratio to receive alendronate (10 mg/day) and calcium carbonate (500 mg/day) or calcium carbonate alone for 6 months. We measured serum markers of bone formation (osteocalcin [OC], bone isoform of alkaline phosphatase [BAP], and collagen type I C-terminal propeptide [CICP]) and urinary markers of bone resorption (cross-linked N-telopeptide [NTx], free deoxypyridinoline [iFDpd], and free pyridinolines). All subjects had two measurements 1 week apart at baseline to calculate the short-term variability. Biochemical measurements were then made at 4, 8, 12, 24, and 25 weeks. Measurements of bone mass were made by dual-energy X-ray absorptiometry (DXA) at the lumbar spine and proximal femur twice at baseline and then at 24 and 25 weeks. The mean difference in change in BMD and markers between both groups at the end of the study that were significant were (short-term variability in brackets): DXA total hip 4.3% (2.5%), NTX 49% (10%), iFDpd 22% (12%), OC 28% (13%), BAP 31% (13%), and CICP 31% (11%). Five of the six markers showed significant responses to alendronate therapy, but they differed in the relationship between size of response and variability. These biochemical markers performed better than DXA for monitoring alendronate therapy over 6 months.

Aged↗

Pharmacokinetics and concentration-effect relationships of therapeutic monoclonal antibodies and fusion proteins.

Although monoclonal antibodies (mAbs) constitute a major advance in therapeutics, their pharmacokinetic (PK) and pharmacodynamic (PD) properties are not fully understood. Saturable mechanisms are thought to occur in distribution and elimination of mAbs, which are protected from degradation by the Brambell's receptor (FcRn). The binding of mAbs to their target antigen explains part of their nonlinear PK and PD properties. The interindividual variability in mAb PK can be explained by several factors, including immune response against the biodrug and differences in the number of antigenic sites. The concentration-effect relationships of mAbs are complex and dependent on their mechanism of action. Interindividual differences in mAb PD can be explained by factors such as genetics and clinical status. PK and concentration-effect studies are necessary to design optimal dosing regimens. Because of their above-mentioned characteristics, the interindividual variability in their dose-response relationships must be studied by PK-PD modelling.

Animals↗

[Tumor characteristics and five-year survival in breast cancer patients at the National Cancer Institute, Rio de Janeiro, Brazil].

Numerous factors have been studied to establish more secure prognostic criteria in breast cancer patients. This study estimates five-year survival rates and principal prognostic factors related to tumor characteristics in women with invasive breast cancer and submitted to surgery at the National Cancer Institute, Rio de Janeiro, Brazil, from May 1995 to July 1996. Study variables were: lymph node status, tumor size, aggressiveness grade, and presence of estrogen and progesterone receptors. Survival functions were calculated according to the Kaplan-Meyer method. The Cox proportional hazards model was used to evaluate prognostic factors. Five-year survival was 75% for all women and 64% for those with node involvement. Multivariate analyses identified node involvement as the strongest predictor of outcome; a positive estrogen receptor test was associated with a better prognosis. These findings highlight the need for studies to assess new variables to be added to known factors in order to better orient therapy for breast cancer.

Adult↗

A structured review of the relationship between microalbuminuria and cardiovascular events in patients with diabetes mellitus and hypertension.

STUDY OBJECTIVE: To quantify the relative risk of cardiovascular events associated with microalbuminuria in patients with both diabetes mellitus and hypertension. DESIGN: A structured literature search from January 1990-December 2002 using MEDLINE, IPA, and CINAHL. MEASUREMENTS AND MAIN RESULTS: We identified original studies that reported the presence or absence of microalbuminuria and estimates of risk associated with cardiovascular events in patients with both diabetes and hypertension. Abstracted information consisted of study design, patient demographics and risk factors, treatment regimens, and outcome variables. Point estimates and confidence intervals for relative risk were calculated from available data. Of 651 citations identified and reviewed based on title and abstract, 72 were selected for full review. Seven met the inclusion criteria. Because of lack of homogeneity among studies, the results were not conducive to pooling. Cardiovascular end points associated with the presence of microalbuminuria in these studies were all-cause mortality, cardiovascular mortality, and composite cardiovascular morbidity. The relative risk of cardiovascular end points associated with the presence of microalbuminuria ranged from 1.6 (95% confidence interval [CI] 1.2-2.2) to 7.9 (95% CI 2.5-25.3). CONCLUSION: From the limited information available, the risk of cardiovascular events and mortality is estimated to be 2-8 times higher when microalbuminuria is present in patients with diabetes and hypertension. Point estimates in relative risk of cardiovascular morbidity and mortality in patients with diabetes and hypertension were generally higher compared with studies estimating risk in those with only diabetes. Studies that examine the relationship between microalbuminuria (scaled as a continuous or ordinal variable) and cardiovascular events are necessary to clarify potential benefits of pharmacotherapies that reduce levels of urinary albumin.

Albuminuria↗