Minimal residual disease and outcome characteristics in infant KMT2A-germline acute lymphoblastic leukaemia treated on the Interfant-06 protocol

BACKGROUND

The outcome of infants with KMT2A-germline acute lymphoblastic leukaemia (ALL) is superior to that of infants with KMT2A-rearranged ALL but has been inferior to non-infant ALL patients. Here, we describe the outcome and prognostic factors for 167 infants with KMT2A-germline ALL enrolled in the Interfant-06 study.

METHODS

Univariate analysis on prognostic factors (age, white blood cell count at diagnosis, prednisolone response and CD10 expression) was performed on KMT2A-germline infants in complete remission at the end of induction (EOI; n = 163). Bone marrow minimal residual disease (MRD) was measured in 73 patients by real-time quantitative polymerase chain reaction at various time points (EOI, n = 68; end of consolidation, n = 56; and before OCTADAD, n = 57). MRD results were classified as negative, intermediate (<5∗10^-4), and high (≥5∗10^-4).

RESULTS

The 6-year event-free and overall survival was 73.9% (standard error [SE] = 3.6) and 87.2% (SE = 2.7). Relapses occurred early, within 36 months from diagnosis in 28 of 31 (90%) infants. Treatment-related mortality was 3.6%. Age <6 months was a favourable prognostic factor with a 6-year disease-free survival (DFS) of 91% (SE = 9.0) compared with 71.7% (SE = 4.2) in infants >6 months of age (P = 0.04). Patients with high EOI MRD ≥5 × 10^-4 had a worse outcome (6-year DFS 61.4% [SE = 12.4], n = 16), compared with patients with undetectable EOI MRD (6-year DFS 87.9% [SE = 6.6], n = 28) or intermediate EOI MRD <5 × 10^-4 (6-year DFS 76.4% [SE = 11.3], n = 24; P = 0.02).

CONCLUSION

We conclude that young age at diagnosis and low EOI MRD seem favourable prognostic factors in infants with KMT2A-germline ALL and should be considered for risk stratification in future clinical trials.

Skeletal maturation, fundamental motor skills, and motor performance in preschool children

Relationships among skeletal age (SA), body size and fundamental motor skills (FMS) and motor performance were considered in 155 boys and 159 girls 3-6 years of age. Stature and body mass were measured. SA of the hand-wrist was assessed with the Tanner-Whitehouse II 20 bone method. The Test of Gross Motor Development, 2nd edition (TGMD-2), and the Preschool Test Battery were used, respectively, to assess FMS and motor performance. Based on hierarchical regression analyses, the standardized residuals of SA on chronological age (SAsr) explained a maximum of 6.1% of the variance in FMS and motor performance in boys (ΔR² ₃ , range 0.0%-6.1%) and a maximum of 20.4% of the variance in girls (ΔR² ₃ , range 0.0%-20.4%) over that explained by body size and interactions of SAsr with body size (step 3). The interactions of the SAsr and stature and body mass (step 2) explained a maximum of 28.3% of the variance in boys (ΔR² ₂ , range 0.5%-28.3%) and 16.7% of the variance in girls (ΔR² ₂ , range 0.7%-16.7%) over that explained by body size alone. With the exception of balance, relationships among SAsr and FMS or motor performance differed between boys and girls. Overall, SA per se or interacting with body size had a relatively small influence in FMS and motor performance in children 3-6 years of age.

Diagnosis of Glaucoma by Indirect Classifiers

Objectives: Demonstration of the applicability of a framework called indirect classification to the example of glaucoma classification. Indirect classification combines medical a priori knowledge and statistical classification methods. The method is compared to direct classification approaches with respect to the estimated misclassification error.

Methods: Indirect classification is applied using classification trees and the diagnosis of glaucoma. Misclassification errors are reduced by bootstrap aggregation. As direct classification methods linear discriminant analysis, classification trees and bootstrap aggregated classification trees are utilized in the problem of glaucoma diagnosis. Misclassification rates are estimated via 10-fold cross-validation.

Results: Indirect classification techniques reduce the misclassification error in the context of glaucoma classification compared to direct classification methods.

Conclusions: Embedding a priori knowledge into statistical classification techniques can improve misclassification results. Indirect classification offers a framework to realize this combination.

Simulation Based Analysis of Automated Classification of Medical Images

Objectives: The ability of various classifiers to discriminate between normal and glaucomatous eyes based on features derived from automated analysis of laser scanning images of the eye background is investigated.

Methods: To compare the classifiers without over-optimization for a given dataset, we use a simulation model to create topography images. We designed three different simulation setups as model of extreme situations and medical subgroups.

Results: Neither linear nor tree-based classifiers are ideal for all setups. The most robust performance is obtained by a combination of both, so-called Double-Bagging. Classification of real data from a case-control study shows best results with Double-Bagging. All results obtained with the analysis method extracting features automatically are worse than those obtained by the same classifiers but with features derived from an analysis method that requires intervention of a physician.

Conclusions: Robust classification results for classification of laser scanning images obtained with the Heidelberg Retina Tomograph are achieved by combined classifiers. The examined automated procedure causes an increased misclassification error compared to the established clinical routine requiring an expert physician’s intervention.

Comparison of Classifiers Applied to Confocal Scanning Laser Ophthalmoscopy Data

Objectives: Comparison of classification methods using data of one clinical study. The tuning of hyperparameters is assessed as part of the methods by nested-loop cross-validation.

Methods: We assess the ability of 18 statistical and machine learning classifiers to detect glaucoma. The training data set is one case-control study consisting of confocal scanning laser ophthalmoscopy measurement values from 98 glaucoma patients and 98 healthy controls. We compare bootstrap estimates of the classification error by the Wilcoxon signed rank test and box-plots of a bootstrap distribution of the estimate.

Results: The comparison of out-of-bag bootstrap estimators of classification errors is assessed by Spearman’s rank correlation, Wilcoxon signed rank tests and box-plots of a bootstrap distribution of the estimate. The classification methods random forests 15.4%, support vector machines 15.9%, bundling 16.3% to 17.8%, and penalized discriminant analysis 16.8% show the best results.

Conclusions: Using nested-loop cross-validation we account for the tuning of hyperparameters and demonstrate the assessment of different classifiers. We recommend a block design of the bootstrap simulation to allow a statistical assessment of the bootstrap estimates of the misclassification error. The results depend on the data of the clinical study and the given size of the bootstrap sample.

Polymorphisms in the ABCB1 gene and effect on outcome and toxicity in childhood acute lymphoblastic leukemia

The membrane transporter P-glycoprotein, encoded by the ABCB1 gene, influences the pharmacokinetics of anti-cancer drugs. We hypothesized that variants of ABCB1 affect outcome and toxicity in childhood acute lymphoblastic leukemia (ALL). We studied 522 Danish children with ALL, 93% of all those eligible. Risk of relapse was increased 2.9-fold for patients with the 1199GA variant versus 1199GG (P=0.001), and reduced 61% and 40%, respectively, for patients with the 3435CT or 3435TT variants versus 3435CC (overall P=0.02). The degree of bone marrow toxicity during doxorubicin, vincristine and prednisolone induction therapy was more prominent in patients with 3435TT variant versus 3435CT/3435CC (P=0.01/P<0.0001). We observed more liver toxicity after high-dose methotrexate in patients with 3435CC variant versus 3435CT/TT (P=0.03). In conclusion, there is a statistically significant association between ABCB1 polymorphisms, efficacy and toxicity in the treatment of ALL, and ABCB1 1199G>A may be a new possible predictive marker for outcome in childhood ALL.

[Prevalence of glaucomatous optic nerve atrophy among a working population in Germany diagnosed by a telemedical approach]

PURPOSE

The aim of this study was to determine the prevalence of glaucomatous optic nerve atrophy among a working population in Germany by secondary evaluation of a study conducted to estimate the prevalence of retinal microangiopathic abnormalities by telemedical examination of the retina.

PATIENTS AND METHODS

From August 2002 until January 2004 the retina and optic nerve head were examined in 19,294 Caucasians using a non-mydriatic fundus camera (Kowa, nonmyd-alpha 45), which produces colour images with 45 degrees. The images of the retina and optic nerve head were evaluated telemedically by glaucoma specialists in respect to optic nerve pathologies and microangiopathic abnormalities by a standardised procedure. Glaucomatous optic nerve atrophy was diagnosed when specific glaucomatous morphological alterations of the optic nerve head were present. A complete medical history including reported elevated intraocular pressure (IOP) and blood pressure was obtained.

RESULTS

The intra-observer and inter-observer reliability were 0.884 and 0.740, respectively. Cronbach's alpha for two evaluation cycles each of two observers was 0.870. The prevalences of glaucomatous optic nerve atrophy in the different age groups were 0.07 % (45 - 49 years), 0.40 % (50 - 54 years), 0.45 % (55 - 59 years) and 0.82 % (60 - 64 years). Age could be established as an important risk factor for glaucomatous optic nerve atrophy, while no influence of gender or family history was found.

CONCLUSION

Telemedical evaluation of colour images of the retina and optic nerve acquired by a non-mydriatic fundus camera allows a fast and efficient screening of many subjects with medium reliability.

The degree of myelosuppression during maintenance therapy of adolescents with B-lineage intermediate risk acute lymphoblastic leukemia predicts risk of relapse

Drug doses, blood levels of drug metabolites and myelotoxicity during 6-mercaptopurine/methotrexate (MTX) maintenance therapy were registered for 59 adolescents (>or=10 years) and 176 non-adolescents (<10 years) with B-cell precursor acute lymphoblastic leukemia (ALL) and a white blood cell count (WBC) <50 x 10(9)/l at diagnosis. Event-free survival was lower for adolescents than non-adolescents (pEFS(12y):0.71 vs 0.83, P=0.04). For adolescents staying in remission, the mean WBC during maintenance therapy (mWBC) was related to age (r(S)=0.36, P=0.02), which became nonsignificant for those who relapsed (r(S)=0.05, P=0.9). The best-fit multivariate Cox regression model to predict risk of relapse included mWBC and thiopurine methyltransferase activity, which methylates mercaptopurine and reduces the intracellular availability of cytotoxic 6-thioguanine nucleotides (coefficient: 0.11, P=0.02). The correlation of mWBC to the risk of relapse was more pronounced for adolescents (coefficient=0.65, P=0.003) than for non-adolescents (coefficient=0.42, P=0.04). Adolescents had higher mean neutrophil counts (P=0.002) than non-adolescents, but received nonsignificantly lower mercaptopurine and MTX doses during maintenance therapy. Red blood cell MTX levels were significantly related to the dose of MTX among adolescents who stayed in remission (r(S)=0.38, P=0.02), which was not the case for those who developed a relapse (r(S)=0.15, P=0.60). Thus, compliance to maintenance therapy may influence the risk of relapse for adolescents with ALL.

[Time-multiplexing stereophotography: 2D and 3D qualitative and semiquantitative evaluation of glaucomatous optic disc atrophy]

PURPOSE

Real color documentation of the optic nerve head (ONH) is one of the most important methods in identifying early progression of glaucomatous optic nerve damage. This study qualitatively and semiquantitatively compared the evaluation of ONH photographs, using a 3D time-multiplexing system and conventional 2D photography, visualized on a computer monitor.

PATIENTS AND METHODS

Twelve 15 degrees sequential stereophotographs from the Erlangen Glaucoma Registry were scanned by a SprintScan 35 Plus Film scanner (Polaroid, Waltham, MA, USA) and converted by computer software (3D-PIX, NuVision, McNaughton Inc., Beaverton, OR, USA) in jps format (3D). The same ONH images were shown in 2D and 3D to 22 subjects: 12 residents and ten ophthalmologists and evaluated using a standardized questionnaire.

RESULTS

We observed a significantly better evaluation with stereoscopic pictures for both qualitative parameters (cup depth, visibility of the retinal nerve fibers, and the thinnest location of the neuroretinal rim) and quantitative parameters (c/d ratio and size of the disc, depending on the training level: in 3D better evaluation by the residents, in 2D by the ophthalmologists). With 2D pictures, we found better evaluation of the B zone and the stage of atrophy. Other than the method used for the entire evaluation, there was no significant difference between the groups. For the parameters weighed for clinical importance, the score of correct answers was significantly better with stereoscopic pictures.

CONCLUSION

This study showed a significantly better evaluation of glaucomatous ONH atrophy with 3D images than with 2D pictures, independently of the evaluators' clinical training level. The computer-based evaluation of ONH atrophy using a time-multiplexing system (shutter glasses) may improve the diagnosis of glaucoma patients.

FISH studies on the telomeric regions of the T-cell acute lymphoblastic leukemia cell line CCRF-CEM

So far, the problem of an influence of translocations on the telomeres of the involved chromosomes has not been addressed yet in human cells. Therefore, the telomeres of a karyotypically rather well characterized T-cell acute lymphoblastic leukemia (T-ALL) cell line (CCRF-CEM) with several marker chromosomes were examined using peptide nucleic acid (PNA) telomere FISH probes to compare the telomere length of these markers with that of the chromosome arms of their origin. In addition, chromosome libraries, centromeric probes, and subtelomeric DNA probes were used to further define the marker chromosomes. Two markers could be newly defined and a concise karyotype of the cell line could be obtained by these detailed examinations: 42-47,X,-X,del(5) (q35?),t(5;15)(q14;q13.2),t(8;9)(p11;p24),del(9)(:p13-->qter)/inv(9)(pter-->p12::q21-->p12::q21-->qter),+13,+20,+der(22)(p+ [HSR?])[cp]. The relative telomere length of all chromosomes showed considerable interchromosomal, intercellular, and inter-passage variation. However, it could be shown, that in four different passages of the examined cell line the observed differences between relative telomere lengths of the markers and the chromosomes of their origin, with two exceptions (short arms of del/inv9 and der22), were not significant. On the other hand, because of its mentioned variability, telomere length alone is not sufficient to reliably define the derivation of markers.

Automated segmentation of the optic nerve head for diagnosis of glaucoma

Glaucoma is the second most common cause of blindness worldwide. Low awareness and high costs connected to glaucoma are reasons to improve methods of screening and therapy. A well-established method for diagnosis of glaucoma is the examination of the optic nerve head using scanning-laser-tomography. This system acquires and analyzes the surface topography of the optic nerve head. The analysis that leads to a diagnosis of the disease depends on prior manual outlining of the optic nerve head by an experienced ophthalmologist. Our contribution presents a method for optic nerve head segmentation and its validation. The method is based on morphological operations, Hough transform, and an anchored active contour model. The results were validated by comparing the performance of different classifiers on data from a case-control study with contours of the optic nerve head manually outlined by an experienced ophthalmologist. We achieved the following results with respect to glaucoma diagnosis: linear discriminant analysis with 27.7% estimated error rate for automated segmentation (aut) and 26.8% estimated error rate for manual segmentation (man), classification trees with 25.2% (aut) and 22.0% (man) and bootstrap aggregation with 22.2% (aut) and 13.4% (man). It could thus be shown that our approach is suitable for automated diagnosis and screening of glaucoma.

Does the distance to normal renal parenchyma (DTNRP) in nephron-sparing surgery for renal cell carcinoma have an effect on survival?

BACKGROUND

The effect of the distance to normal renal parenchyma (DTNRP) on survival after nephron-sparing surgery (NSS) for renal cell cancer (RCC) was analyzed. Additionally, the role of T-classification, tumor diameter and tumor grading was considered.

PATIENTS AND METHODS

NSS was performed on 126 patients with RCC between 1988 and 2000. Eighty-six patients were submitted to annual follow-up. These 86 patients were sub-classified into statistical groups according to the distance to normal renal parenchyma (< or = 2mm; > 2mm - < or = 5mm; >5 mm), T-classification, tumor diameter (< or = 20mm; > 20mm - < or = 30 mm; >30 mm - < or = 50mm; > 50mm) and tumor grading. The effect of belonging to one of these groups on survival was analyzed using the Log-Rank-Test (SPSS; version 11.0) and the Kaplan and Meier survival data. The level of significance was set at p < 0.05.

RESULTS

During the follow-up period, 4 patients died related to RCC and 15 patients died from other causes. The tumor-specific survival was 95.4%. At the end of 2002, the mean follow-up time was 5.5 years (range 0.1 - 14.7). None of the variables which had been analyzed in our statistical groups had an effect on the overall survival.

CONCLUSION

The distance to normal renal parenchyma does not influence survival, suggesting an additional resection to be unnecessary even in cases where the DTNRP is reported by frozen section to be less than 2 mm. RCC up to 5 cn in tumor diameter can be safely removed by NSS, even in the presence of a functional intact contralateral kidney.

Simulation based analysis of automated, classification of medical images

OBJECTIVES

The ability of various classifiers to discriminate between normal and glaucomatous eyes based on features derived from automated analysis of laser scanning images of the eye background is investigated.

METHODS

To compare the classifiers without over-optimization for a given dataset, we use a simulation model to create topography images. We designed three different simulation setups as model of extreme situations and medical subgroups.

RESULTS

Neither linear nor tree-based classifiers are ideal for all setups. The most robust performance is obtained by a combination of both, so-called Double-Bagging. Classification of real data from a case-control study shows best results with Double-Bagging. All results obtained with the analysis method extracting features automatically are worse than those obtained by the same classifiers but with features derived from an analysis method that requires intervention of a physician.

CONCLUSIONS

Robust classification results for classification of laser scanning images obtained with the Heidelberg Retina Tomograph are achieved by combined classifiers. The examined automated procedure causes an increased misclassification error compared to the established clinical routine requiring an expert physician's intervention.

Comparison of tree-based methods for prognostic stratification of survival data

Tree-based methods can be used to generate rules for prognostic classification of patients that are expressed as logical combinations of covariate values. Several splitting algorithms have been proposed for generating trees from survival data. However, the choice of an appropriate algorithm is difficult and may also depend on clinical considerations. By means of a prognostic study of patients with gallbladder stones and of a simulation study, we compare the following splitting algorithms: log-rank statistic adjusted for measurement scale with (AP) and without (AU) pruning, exponential log-likelihood loss (EP), Kaplan-Meier (KP) distance of survival curves, unadjusted log-rank statistic (LP), martingale residuals (MP), and node impurity (ZP). With the exception of the AU algorithm (based on a Bonferroni-adjusted p-value driven stopping rule), trees are pruned using the measure of split-complexity, and optimally-sized trees are selected using cross-validation. The integrated Brier score is used for the evaluation of predictive models. According to the results of our simulation study and of the clinical example, we conclude that the AU, AP, EP, and LP algorithm may yield superior predictive accuracy. The choice among these four algorithms may be based on the required parsimonity and on medical considerations.

Diagnosis of glaucoma by indirect classifiers

OBJECTIVES

Demonstration of the applicability of a framework called indirect classification to the example of glaucoma classification. Indirect classification combines medical a priori knowledge and statistical classification methods. The method is compared to direct classification approaches with respect to the estimated misclassification error.

METHODS

Indirect classification is applied using classification trees and the diagnosis of glaucoma. Misclassification errors are reduced by bootstrap aggregation. As direct classification methods linear discriminant analysis, classification trees and bootstrap aggregated classification trees are utilized in the problem of glaucoma diagnosis. Misclassification rates are estimated via 10-fold cross-validation.

RESULTS

Indirect classification techniques reduce the misclassification error in the context of glaucoma classification compared to direct classification methods.

CONCLUSIONS

Embedding a priori knowledge into statistical classification techniques can improve misclassification results. Indirect classification offers a framework to realize this combination.

Homocysteine and risk of open-angle glaucoma

Homocysteine levels and the frequency of heterozygous methylenetetrahydrofolate reductase (MTHFR) C677T mutation are increased in open-angle glaucoma. Since homocysteine can induce vascular injury, alterations in extracellular matrix remodelling, and neuronal cell death, these findings may have important implications for understanding glaucomatous optic neuropathy.

Urinary calcium excretion in healthy children and adolescents

Urinary calcium (Ca) excretion was determined in 1,578 24-h urine samples from 507 healthy children and adolescents (252 boys, 255 girls; 2.8-18.4 years) participating in the DONALD Study and is presented for 32 different age and sex groups. Calciuria values related to body weight (mg/kg per day) were relatively constant except for a transient decrease during puberty in all centiles, with a later onset in boys than girls. Distribution of calciuria (mg/kg per day) was best normalized by log transformation, with an almost constant standard deviation of the log-transformed values. Ca excretion was >/=4 mg/kg per day in 8.6% and >/=6 mg/kg per day in 1. 5% of the urine samples. Based on Ca excretion rates of 1,080 pairs of 24-h urine samples from 364 children and adolescents, sensitivity, specificity, and the predictive value for hypercalciuria (>/=4 mg/kg per day) in the next urine sample were calculated at three test levels classifying calciuria of the initial urine sample. In summary, this study presents normal values of urinary Ca excretion related to age and sex in a population of healthy German children and adolescents consuming a typical western-style diet. A high level of calciuria in a random urine sample is important in the diagnosis of hypercalciuria.

Development of scores to measure the effects of nutrition counselling on the overall diet: A pilot study in children and adolescents

An intervention study by documented dietary counselling was carried out in a sample of 9 children and adolescents (12-15 years) living in a full-time institution in Dortmund. Three weighed dietary records were collected over 3-7 days, one before and one after each of two individual nutrition counselling sessions, which were based on the recommended intake of food groups defined by the Optimized Mixed Diet (OMD), a quantitative preventive dietary conception for children and adolescents. As univariate dietary parameters (e.g., cholesterol intake), which are often used to show the effectiveness of nutrition counselling, do not take into account the multivariate complexitiy of nutrition, we developed 3 multivariate scores to measure the effectiveness of nutrition counselling. They are defined as: Recommended Food group change Score (RFS): Average change in the amounts of the deviations (%) from the reference food groups values (OMD = 100 %) before and after counselling taking into account the aim (eat mor/less) of the counselling session, exclusively based on the food groups addressed during counselling. Total Food group change Score (TFS): Average change in the amounts of the deviations (%) from the reference food group values (OMD = 100 %) before and after counselling based on all food groups consumed. Nutrient Improvement Score (NIS): Average change in the negative deviations (%) of 8 vitamins and 8 minerals from the German reference values for nutrient intake (Deutsche Gesellschaft für Ernährung (DGE) = 100 %) before and after counselling. On average, the intakes of the food groups mentioned during the first counselling session improved considerably (RFS = +36 %), the change in the intake of all food groups was small (TFS = +6 %) and the nutrient intakes did not improve (NIS = 0 %). From the second counselling session the values of the RFS was +10 %, of the TFS was +6% and of the NIS +3 %. This means that the success of counselling on one dietary criterion does not guarantee success on others. Our food and nutrient based scores together with a detailed food intake assessment give an example of multivariate measurements of nutrition counselling outcomes.

A high-resolution radiation hybrid map of the proximal region of rat chromosome 4

Radiation hybrid (RH) mapping has been used to produce genome maps in the human and mouse, but as yet the technique has been applied little to other species. We describe the use of RH mapping in the rat, using a newly available rat/hamster RH panel, to construct an RH map of the proximal part of rat Chromosome (Chr) 4. This region is of interest because quantitative trait loci (QTLs) for defective insulin and catecholamine action, hypertension, and dyslipidemia map to this region. The RH map includes 23 rat genes or microsatellites previously mapped to this part of Chr 4, one rat gene not previously mapped in the rat, and markers for four new genes, homologs of which map to the syntenic region of the mouse genome. The RH map integrates genetic markers previously mapped on several rat crosses, increases the resolution of existing maps, and may provide a suitable basis for physical map construction and gene identification in this chromosomal region. Our results demonstrate the utility of RH mapping in the rat genome and show that RH mapping can be used to localize, in the rat genome, the homologs of genes from other species such as the mouse. This will facilitate identification of candidate genes underlying QTLs on this chromosomal segment.

Systematic review of case-control studies: oral contraceptives show no effect on melanoma risk

BACKGROUND

Parallel to the rising incidence of malignant melanoma in fair-skinned populations, intensive efforts are currently devoted to identifying risk factors for melanoma in addition to the well-known cutaneous factors and those variables related to UV-exposure.

OBJECTIVE

Systematic review of published results to elucidate the role of oral contraceptives in the development of malignant melanoma.

DATA SOURCES

Literature retrieval systems MEDLINE and CANCERLIT as well as reference lists of already collected studies.

STUDY SELECTION

All 18 (non-duplicate) case-control studies on the above relationship.

DATA EXTRACTION

From the published data, study-specific odds ratios (OR) and accompanying confidence intervals (CI) were recalculated. For a quantitative meta-analytical summarisation two different models have been applied: a "fixed effects" (FE) and a "random effects" (RE) model.

DATA SYNTHESIS

Study-specific ORs ranged from 0.13 up to 1.85; however, the majority of studies (14 of 18) yielded similar ORs within the interval [0.82, 1.15]. The summary ORs estimated from FE- and RE-models were both 0.95 (95% CI: [0.87, 1.04] for the FE-model, [0.87, 1.05] for the RE-model).

CONCLUSION

The systematic review of case-control studies revealed no evidence for an aetiological role of oral contraceptives in the development of malignant melanoma.

Energy intake of 1 to 18 year old German children and adolescents

In a sample of 695 healthy well-nourished German children and adolescents covering the total age range from 1 to 18 years, 3d weighed diet records were collected and measurements of body height and weight were taken. 10% non-plausible records (reported energy intake (EI):estimated basal metabolic rate (BMR) < Cut off 1.06) were excluded from further analysis. The rate of non-plausible records was low in the childhood age groups (2-6%), higher in the male (10%), and highest in the female adolescents (30%). Recalculation of age and sex specific cut offs based on assumed light physical activity levels (PAL) reduced the exclusion rate to 6.5% (total) and 20% (female adolescents). The reported energy intake of the total sample based on plausible records (n = 627, EI:BMR > or = 1.06) was close to the new estimations of energy requirements assuming light physical activity which are proposed for the revision of the current FAO/WHO energy requirements. The sample was of normal height and weight compared to the Netherlands growth references. For a definite interpretation of the low reported energy intake in the context of health promoting physical activity patterns of children and adolescents more scientific evidence should be available.

Antibody response to Haemophilus influenzae type b capsular polysaccharide conjugated to tetanus toxoid in preterm infants

OBJECTIVE

To evaluate the antibody response to a Haemophilus influenzae type b capsular polysaccharide (HibCP) tetanus toxoid (TT) conjugate vaccine (HibCP-TT) in preterm infants.

SUBJECTS

Thirty-five healthy preterm infants with gestational ages (GA) from 27 to 36 weeks and birth weights from 920 to 2550 g. Controls were 37 term infants.

METHODS

All infants were immunized with HibCP-TT at 2, 4 and 12 months of age. Antibodies to HibCP and TT were determined at each immunization and 1 month after the second and third.

RESULTS

After two doses of HibCP-TT the preterm infants with GAs < or = 30 weeks (n = 8; mean GA, 29.5 weeks) had a significantly lower HibCP antibody response than the preterm infants with GAs > 30 weeks (n = 23; mean GA, 34.2 weeks) (P = 0.004), who for their part had a response not significantly different from that of the term infants. After the third dose there were no significant differences among the groups. The response to the TT part of the vaccine showed the same pattern.

CONCLUSION

Although the most immature infants may show an inadequate antibody response to the initial immunizations, many preterm infants can benefit from vaccination with HibCP-TT when starting immunization at the same chronologic age as term infants.

Effects of a high protein intake on renal acid excretion in bodybuilders

Bodybuilders often prefer a high protein diet to achieve maximum skeletal muscle hypertrophy. In this study the effect of a high protein diet on renal acid load and renal handling of proton excretion was studied comparing dietary intake and urinary ionograms in 37 male bodybuilders and 20 young male adults. Energy intake (+ 7%), protein intake (128 vs 88 g/d/1.73 m2), and renal net acid excretion (95 vs 64 mmol/d/1.73 m2) were higher in the bodybuilders than in the controls, however, urine-pH was only slightly lower (5.83 vs 6.12). In the bodybuilders renal ammonium excretion was higher at any given value of urine pH than in the controls. In a regression analysis protein intake proved to be an independent factor modulating the ratio between urine-pH and renal ammonium excretion. The concomitant increase of renal net acid excretion and maximum renal acid excretion capacity in periods of high protein intake appears to be a highly effective response of the kidney to a specific food intake leaving a large renal surplus capacity for an additional renal acid load.

Outcome-oriented cutpoints in analysis of quantitative exposures

In the analysis of epidemiologic data in which exposure has been measured on a continuous scale, cutpoints can be defined to delineate categories or exposure can be modeled as a continuous covariate by assuming a special functional shape of the effect on disease status. Rules for classifying exposure into two or more categories range from a priori selection of cutpoints to data-oriented rules. The risk estimates may vary, however, with the choice of cutpoint. If the cutpoint selected is that for which the most impressive effect of exposure on outcome is observed, the final result must be qualified by adjustment. In this paper, the authors propose a method for adjusting results which are derived by varying the cutpoint on a specified selection interval. Adjustment is derived from the null distribution of the maximally selected test statistic. The method should be applied to correct p values if the cutpoint used to define different levels of exposure is selected in such a way that the measure of difference between two risk groups, such as the odds ratio or relative risk, is maximized. No method is yet available for adjusting the resulting risk estimate and the corresponding confidence limits. The authors illustrate the statistical method by applying it to data from a case-control study of the association between exposure to magnetic fields and risk of cancer in children which was conducted recently in Denmark.