Minding Your “ps and qs” When Using Forced-Choice Recognition Tests

Denney (1996), and Frederick, Carter, and Powel (1995) described a forced-choice recognition test (FCRT) to evaluate suspicious complaints of remote memory loss. Although the two-alternative forced-choice trials in symptom validity testing have equal prior probabilities of correct answers (p) and incorrect answers (q), ps and qs might vary from 0.5 on individual trials of FCRTs. FCRTs nonetheless remain conservative procedures for evaluating suspicious memory loss, as long as the overall p approximates 0.5. In computer simulations, distributions in which p q 0.5 resulted in more conservative decision making than distributions in which p = q = 0.5. The authors demonstrate the ease in constructing FCRTs with overall p = 0.5 and discuss the proper application of FCRT findings in a clinical evaluation.     

Determining reference ('normal') limits in medicine: an application

We provide an account of a study to assess reference limits for eight routine laboratory determinations at the Academic Hospital of the Free University, Amsterdam and emphasize methodological issues rather than results. We argue that reference limits have use mainly in the first phase of the diagnostic process. Reference and target populations should be grossly comparable, and therefore patients (after slight selection) could well serve as references. However, we found major differences between in- and out-patients, so we suggest that this factor, together with age and sex, be taken into account. To arrive at reliable limits, the size of the reference sample should be at least 100. Laboratory reports should provide percentiles, which enable a more flexible decision than do fixed limits.     

Blood Pressure Regulation Across Pregnancy: Evidence of a Paradigm Shift in Gene Expression

Objectives: The authors aimed to provide evidence for a major gene effect on blood pressure across normal pregnancy. Methods: Blood pressure measurements from 265 patients of Mexican descent derived from medical records were grouped into 4-week blocks by gestational age. Analyses of normality in the distribution of measurements for each block were applied to determine the emergence of a major gene effect and identify the gestational age at which that occurs. Systolic and diastolic blood pressures were used to determine median and percentile values for each block. Results: There was a shift from normal to non-normal distribution in systolic blood pressure between 12 and 15 weeks' gestation. This was similar for diastolic blood pressure. Median blood pressure values increased from 10 to 40 weeks' gestation without evidence of a decline during the second trimester of pregnancy. Conclusion: Genetic regulation of blood pressure across pregnancy is dynamic, as demonstrated by the emergence of a major gene effect beginning around 12 weeks' gestation.     

Growth charts for prepubertal children with chronic renal failure due to congenital renal disorders

Despite the high prevalence of and therapeutic attention to growth failure in children with chronic renal failure (CRF), systematic evaluation of spontaneous growth in CRF are lacking. Therefore, we collected retrospectively longitudinal growth and biochemical data in 321 prepubertal patients treated for CRF due to congenital renal disorders. Data were recorded at 3-month intervals during the first 2 years of life and 6-monthly thereafter, up to the age of 10 years. Around 100 measurements were available per age interval. Mixed-longitudinal percentile curves of height and height velocity were constructed. Moreover, a statistical comparison with the heights and height velocities of healthy children and an evaluation of the effect of biochemical parameters on growth was performed. The CRF children had normal heights at birth but dropped below the 3rd normal percentile during the first 15 months of life. Thereafter, growth patterns usually were percentile parallel, with a mean height standard deviation score (SDS) of –2.37±1.6. Height velocities were consistently lower in patients with glomerular filtration rates (GFRs) below onethird of the lower normal limit (25 ml/min per 1.73 m² for patients >1 year) than in patients with better renal function. This difference in growth rates resulted in a mean height SDS of –1.65±1.5 SDS and –2.79±1.4 SDS (age 1–10 years) in the subgroups with relatively better and worse GFR, respectively. Regression analysis confirmed that GRF was a weak but significant predictor of height velocity SDS in most age groups.Study group members: I. Rätsch (Ancona), K. Michelis, T. Kapogiannis (Athens), F. Jung, T. Lennert (Berlin I), S. Gellert (Berlin II), T. Tulassay, P. Sallay (Budapest), T. von Lilien, D. Michalk (Cologne), M.-A. von Wendt-Göknur (Erlangen), K. E. Bonzel (Essen), R. Gusmano, E. Verrina (Genova), G. Offner (Hannover), O. Mehls, A.-M. Wingen, C. Fabian-Bach (Heidelberg, coordinators), A. Appiani, A. Bettinelli (Milan), J. Feber (Prague), G. Rizzoni, S. Picca (Rome), H. J. Stolpe, M. Wigger (Rostock), J. Kist-van Holthe, E. Wolff (Rotterdam, coordinators for the centers Amsterdam, Antwerp, Groningen, Nijmegen, Rotterdam), U. Berg (Stockholm), M. Fischbach (Strasbourg), E. Dobos (Szeged), E. Balzar (Vienna), T. Neuhaus (Zurich).     

Estimating reference ranges in clinical pathology: an objective approach

Conventional reference ranges evolve from subjective criteria for health and disease. We offer an objective method for distinguishing typical from atypical values by purely statistical criteria. We define typical values as those exhibiting a linear relationship with percentiles on a value versus percentile plot. Identification of percentiles at which deviation from linearity occurs results from calculation of correlation coefficients between values and percentiles over centrally expanding ranges of percentiles. One selects arbitrarily some minimum value for these correlation coefficients, for example, 0.990, as the criterion for deviation from linearity. Values encompassed by these percentiles of deviation constitute an objective reference range. Identification of any correlations between atypical values and symptoms of disease requires clinical follow-up studies.     

Waist circumference percentiles for 7- to 17-year-old Turkish children and adolescents

Abdominal obesity is associated with risk of cardiovascular disease and type 2 diabetes mellitus. Waist circumference as a measure of obesity may be clinically useful as a predictor of metabolic syndrome in children. To develop age- and sex-specific reference values for waist circumference we evaluated the data obtained from Turkish children and adolescents. Waist circumference measurements from 4,770 healthy schoolchildren were obtained. Smoothed percentile curves were produced by the LMS method. The median curves of Turkish children were compared with four other countries: Australia, the UK, USA (Bogalusa) and Japan. Smoothed percentile curves and values for the 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th and 97th percentiles were calculated for boys and girls. We found that waist circumference increased with age both in boys and girls. The 50th percentile waist circumference curve of Turkish children was over the British and Japanese but lower than the Bogalusa children and adolescents. This study presents data and smoothed percentile curves for waist circumference of healthy Turkish children aged 7–17 years. The differences in waist circumference of different countries can be explained by lifestyles and cultural characteristics. These data can be added to the existing international reference values for waist circumference of children and adolescents.     

上海市区0~18岁年龄别身高及体重标准研制

[目的]建立上海市区0~18岁男女年龄别身高及体重百分位及Z分法参考值。[方法]采用分层整群随机抽样方法,收集上海市区0~19岁儿童96 104例(男48 790例,女47 314例)的性别、出生年月及1999—2002年身高和体重测量资料。应用LMS方法建立上海市男女童年龄别身高(HFA)及体重(WFA)参考值。[结果]获得了上海市区0~18岁男女年龄别体重及身高7条百分位参考值和相应曲线,即P3、P5、P10、P50、P90、P95和P97;及Z分法±1s、±2s及±3s的参考标准。上海市区0~18岁男性的HFA中位数依次为50.1、77.2、88.7、96.6、103.8、110.9、117.5、123.5、129.2、134.7、139.9、145.5、152.5、160.1、166.4、170.8、173.2、174.1及174.2 cm。女性的HFA中位数依次为49.8、75.6、87.4、95.4、102.6、109.8、116.6、122.4、128.1、134.2、140.4、146.8、153.1、157.6、159.9、161.3、162.0、162.1及162.3 cm。上海市区0~18岁男性的WFA中位数依次为3.4、10.6、12.9、14.7、16.8、19.1、21.7、24.6、27.6、30.8、34.3、38.3、43.4、49.1、54.3、58.6、61.8、63.9及65.1 kg。女性的WFA中位数依次为3.3、9.9、12.2、14.3、16.2、18.4、20.9、23.3、25.8、29.0、32.6、37.1、42.0、46.2、49.0、50.8、52.0、52.4及52.6 kg。[结论]建立了上海市区0~18岁男女百分位、中位数百分比及Z分法3套参考标准。