How many subjects are needed in a longitudinal birth cohort study?

One of the first decisions that needs to be taken when planning a birth cohort concerns the size of the study. This in turn will depend on the research questions to be answered and thence whether environmental exposures and outcomes are measured on a continuum or as dichotomous variables. Here we describe ways in which different birth cohorts have addressed this issue and explore the advantages of smaller detailed studies over larger less-detailed studies.     

Travel distance, age, and sex as factors in follow-up visit compliance in the post-gastric bypass population

BACKGROUND: There is no consensus regarding the optimal rate of follow-up in the post-bariatric surgery patient population. METHODS: The records of all patients who underwent laparoscopic Roux-en-Y gastric bypass from 2001 to 2003 were reviewed. Using patient zip codes, travel distances were calculated between the patients' places of residence and our clinic. Patients were then assigned to 1 of 3 cohorts according to the following distances: (1) < 50 miles, (2) 50 to 100 miles, and (3) > 100 miles. Patient compliance with follow-up appointments at 3 weeks, 3 months, 6 months, 9 months, and 12 months was analyzed. Linear trends were identified using the Mantel-Haenszel test. Age and sex were analyzed as possible predictors of compliance using the chi(2) test. P values < .05 were considered statistically significant. RESULTS: The study group comprised 150 patients (127 females and 23 males). The 3 cohorts contained 115, 21, and 14 patients, respectively. All patients in each cohort were compliant with the 3-week follow-up appointment. Although there were differences in compliance between cohorts at each of the remaining appointments, only the 9-month (70.3% vs 61.9% vs 35.7%) visit showed statistical significance (P = .035). The 6-month visit trended toward significance (85.2% vs 76.2% vs 64.3%; P = .088). Males were more likely to be compliant with the 12-month follow-up (P = .040). When controlling for sex, travel distance was also a predictor of compliance at this follow-up visit (P = .024). Age was not predictive of compliance (P = .827). CONCLUSION: Based on our findings, we conclude that travel distance from the clinic does not significantly affect compliance at the initial follow-up, 3-month, and 12-month appointments. However, distance does tend to affect compliance at the 6-month appointment and significantly affects compliance at the 9-month appointment. Males are more likely to be compliant at the 12 month follow-up visit. We must continue to strive for 100% follow-up in our post-bariatric surgery patients.     

Improved estimates of discordance ratios in twin studies

In the study of monozygotic twins relative to disease and risk factors, particular interest focuses on the subset who are discordant for some suspected risk factor (for example, smoking), since such twins constitute a natural case-control pair. In such studies, questionnaires designed to identify the status of all twin pairs are sometimes error prone and can yield misleading estimates of the concordance-discordance ratios. Greater efforts to verify the characteristics of apparently discordant pairs than to verify those of apparently concordant pairs can result in the 'unequal ascertainment' fallacy. Using the results of a questionnaire with known error rates and the 'apparent' frequencies yielded, we present unbiased, maximum likelihood estimates of the 'true' proportions of concordant and discordant pairs. concordant and discordant pairs. We also present approximate covariances among these estimates.     

Tape stripping of human stratum corneum yields cell layers that originate from various depths because of furrows in the skin

Received: 21 November 1996     

Comorbidity and social phobia: evidence from clinical,epidemiologic, and genetic studies

This paper reviews evidence from clinical, epidemiologic, and family studies regarding the association between social phobia and other syndromes. Social phobia is strongly associated with other anxiety disorders, substance abuse, and affective disorders in both clinical and community samples. An average of 80% of social phobics identified in community samples meet diagnostic criteria for another lifetime condition. Social phobia is most strongly associated with other subtypes of anxiety disorders, with an average of 50% of social phobics in the community reporting a concomitant anxiety disorder including another phobic disorder, generalized anciety, or panic disorder. Approximately 20% of subjects in the community meet lifetime criteria for a major depressive disorder. The onset of social phobia generally precedes that of all other disorders, with the exception of simple phobia. Both clinical severity and treated prevalence are consistently greater among social phobics with comorbid disorders The results of family and twin studies reveal that shared etiologic factors explain a substantial proportion of the comorbidity between social phobia and depression, whereas the association between social phobia and alcoholism derives from a nonfamilial causal relationship between the two conditions. Clinical and phenomenologic implications of these findings are discussed.     

干性型老年黄斑变性60例随访观察

探刊干性型老年黄斑变性（age-related macular deganeration，AMD)的病变发展特征并 寻找监测AMD病情进展的较敏感指标。 方法：用眼底彩色照相和眼底荧光血管造影(FFA)、明视视网膜电囤(ERG)、FM100-hue 色彩试验及视力检查，对60例(111眼)50~80岁、视力≤1.0的干性型AMD患者进行3～74个月(平均30.2个月)的随访观察。 结果：本组68眼经FFA检查、平均25.6个月随访，其中25%的患眼病灶损害有快慢不一的发展．全部111眼视力在平均30.2个月随访中有18%患眼的视力下降2行以下，且与病灶进展相符，FM100-hue 色彩试验的被随访者中，随访2年以后，其总错误分明显的增加(P<0.01)．63眼的明视ERG在随访过程中无明显变化。 结论：大部分干性AMD患眼的病灶损害和视力可以在较长时间内维持稳定。FM100—hue的总错误分可能为监测AMD病情进展的较敏感指标． （中华眼底病杂志，1997，13：150-152）     

抗—HCV阳性单采浆供血员HGV感染随访研究

为了解单采浆供血员庚型肝炎病毒（ＨＧＶ）感染及其转归，对１０２名抗－ＨＣＶ阳性单采浆供血员冻存血清进行抗－ＨＧＶ和ＨＧＶＲＮＡ检测，对抗－ＨＧＶ和（或）ＨＧＶＲＮＡ阳性者作３年随访研究。采用ＥＩＡ法检测抗－ＨＧＶ，包被抗原来自ＨＧＶ不同功能区的合成肽。应用ＲＴ－ＰＣＲ法检测ＨＧＶＲＮＡ，引物选自ＨＧＶＮＳ３区。结果表明，抗－ＨＣＶ阳性单采浆供血员ＨＧＶＲＮＡ阳性率为１９．６１％（２０／１０２），抗－ＨＧＶ阳性率为１７．６５％（１８／１０２），ＨＧＶ感染率（抗ＨＧＶ和／或ＨＧＶＲＮＡ阳性）为２４．５１％（２５／１０２），而对照组仅为０．９４％（１／１０６）。提示单采血浆是ＨＧＶ感染的重要危险因素。ＨＧＶＲＮＡ和抗－ＨＧＶ的３年阴转率分别为３５．００％（７／２０）和１１．１１％（２／１８），说明ＨＧＶ感染有慢性携带趋势     

Effects of MPP+ on catecholamine levels in adrenal glands and heart of rats

The effects of MPP⁺ (2.5–20 mg/kg) on the adrenal glands and heart were investigated in rats. At various periods after s.c. drug administration the rats were decapitated and tissue catecholamine levels were determined by means of HPLC with electrochemical detection. Adrenal dopamine (DA) levels were reduced at 2–8 h after MPP⁺ administration, but this decrease was followed by an elevation after 16 h and return to the control values after one week. Three successive injections of MPP⁺ caused a statistically significant elevation in adrenal DA, one day, with a tendency to elevation four and seven days after the last injection, whereas a severe (up to 96%) decrease in heart noradrenaline (NA) was found one day after the last injection. Seven days after the last injection a 50% depletion of NA in the heart was still observed. Pretreatment with GBR 12909 (30 mg/kg, 4 h) blocked the MPP⁺ (10 mg/kg, 2 h) induced reduction of adrenal DA levels, but at the same time GBR 12909 failed to block the effects of MPP⁺ in the heart. One day after three successive daily injections of MPP⁺ (10 mg/kg each), the DA-uptake inhibitor GBR 12909 (30 mg/kg, 6 h) could still induce an increase in adrenal DA.MPP⁺ appears to lack persistent cytotoxic action in the adrenal medulla but rather to cause a transient inhibition of DA synthesis followed by a compensatory stimulation. The inhibition can be blocked by specific inhibitor of the DA-uptake mechanism, suggesting a direct effect of MPP⁺ taken up by adrenomedullary cells. The data obtained so far do not suggest any involvement of peripheral dopaminergic nerves in the action of MPP⁺ on the adrenal medulla. The long-lasting depletion of the heart NA, however, suggests a lesion of peripheral noradrenergic nerves.Part of this work was presented at 6th International Symposium on Chromaffin Cell Biology, Marburg, Germany, 18–23 August 1991 Correspondence to: M. Kujacic at the above address     

心理学研究中的科学方法与非科学方法

自心理学被界定为一门科学以来 ,对心理学的研究便十分强调研究方法的科学性。那些被认为是不科学的方法 ,如内省、思辨、假设、演绎等被长期排斥在主流心理学的研究方法之外。这虽是学科研究进步的表现 ,但也暴露出心理学研究中唯科学方法的缺陷。由于心理学研究对象的特殊性 ,非科学方法仍是心理学研究中的一种重要方法 ,心理学史上的一些重要成就表明了非科学方法的应用价值。心理学研究中的科学方法与非科学方法并不是对立的。人本主义心理学大胆引进非科学方法 ,兼收并蓄 ,其主张被越来越多的人接受。     

甲磺酸帕珠沙星注射液治疗急性细菌性感染有效性和安全性的多中心临床研究

目的评价甲磺酸帕珠沙星注射液治疗急性细菌性呼吸系统、泌尿生殖系统感染的有效性、安全性。方法采用随机单盲平行对照多中心试验方法。选择急性细菌性呼吸系统、泌尿生殖系统感染患者213例，可评价病例209例，随机编人试验组或对照组。试验组101例．每日1次给予甲磺酸帕珠沙星注射液300mg，iv，gtt，bid；对照组108例，每日1次给予加替沙星注射液200mg，iv，gtt，bid。疗程7～10d。结果甲磺酸帕珠沙星组、加替沙星组有效率分别为94．06％（95／101）和90．74％（98／108）；痊愈率分别为67．33％（68／101）和70．37％（76／108）；细菌清除率分别为94．62％（88／93）和93．62％（88／94）；不良反应发生率分别为7，69％（8／104）和5．50％（6／109）。两组有效性、安全性相似（P〉0．05）。结论甲磺酸帕珠沙星注射液治疗急性细菌性呼吸系统、泌尿生殖系统感染有效、安全，与加替沙星相当。