Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and cost-effectiveness.

OBJECTIVE: To determine the accuracy, acceptability and cost-effectiveness of polymerase chain reaction (PCR) and optical immunoassay (OIA) rapid tests for maternal group B streptococcal (GBS) colonisation at labour. DESIGN: A test accuracy study was used to determine the accuracy of rapid tests for GBS colonisation of women in labour. Acceptability of testing to participants was evaluated through a questionnaire administered after delivery, and acceptability to staff through focus groups. A decision-analytic model was constructed to assess the cost-effectiveness of various screening strategies. SETTING: Two large obstetric units in the UK. PARTICIPANTS: Women booked for delivery at the participating units other than those electing for a Caesarean delivery. INTERVENTIONS: Vaginal and rectal swabs were obtained at the onset of labour and the results of vaginal and rectal PCR and OIA (index) tests were compared with the reference standard of enriched culture of combined vaginal and rectal swabs. MAIN OUTCOME MEASURES: The accuracy of the index tests, the relative accuracies of tests on vaginal and rectal swabs and whether test accuracy varied according to the presence or absence of maternal risk factors. RESULTS: PCR was significantly more accurate than OIA for the detection of maternal GBS colonisation. Combined vaginal or rectal swab index tests were more sensitive than either test considered individually [combined swab sensitivity for PCR 84% (95% CI 79-88%); vaginal swab 58% (52-64%); rectal swab 71% (66-76%)]. The highest sensitivity for PCR came at the cost of lower specificity [combined specificity 87% (95% CI 85-89%); vaginal swab 92% (90-94%); rectal swab 92% (90-93%)]. The sensitivity and specificity of rapid tests varied according to the presence or absence of maternal risk factors, but not consistently. PCR results were determinants of neonatal GBS colonisation, but maternal risk factors were not. Overall levels of acceptability for rapid testing amongst participants were high. Vaginal swabs were more acceptable than rectal swabs. South Asian women were least likely to have participated in the study and were less happy with the sampling procedure and with the prospect of rapid testing as part of routine care. Midwives were generally positive towards rapid testing but had concerns that it might lead to overtreatment and unnecessary interference in births. Modelling analysis revealed that the most cost-effective strategy was to provide routine intravenous antibiotic prophylaxis (IAP) to all women without screening. Removing this strategy, which is unlikely to be acceptable to most women and midwives, resulted in screening, based on a culture test at 35-37 weeks' gestation, with the provision of antibiotics to all women who screened positive being most cost-effective, assuming that all women in premature labour would receive IAP. The results were sensitive to very small increases in costs and changes in other assumptions. Screening using a rapid test was not cost-effective based on its current sensitivity, specificity and cost. CONCLUSIONS: Neither rapid test was sufficiently accurate to recommend it for routine use in clinical practice. IAP directed by screening with enriched culture at 35-37 weeks' gestation is likely to be the most acceptable cost-effective strategy, although it is premature to suggest the implementation of this strategy at present.

Drinking while thirsty can lead to conditioned increases in consumption.

A within-subject design was used to test whether repeatedly drinking a novel-flavoured and coloured drink while thirsty would influence subsequent liking for or consumption of that drink, compared to a different flavoured and coloured drink repeatedly consumed while less thirsty. Each participant was given 300 ml of one flavoured drink (H) after consuming a high salt meal (5.27 g of salt), and 300 ml of another flavoured drink (L) after consuming a low salt meal (1.27 g of salt). Participants had 4 sessions with each meal-type/drink combination, in an intermixed order. Pre- and post-training assessments of the drinks were conducted to determine the impact of the training regime on pleasantness and perceived thirst-quenching effect of the drinks. The final session included a choice test, and ad libitum access to the chosen drink, after either a high or low salt meal. In this final choice session, people drank almost twice as much H as L; however, there were no differential effects of past training on rated liking or choice. The increased consumption of H might reflect greater liking for H which was not detected by the rating scales; or it might reflect the learning of greater "conditioned thirst" in response to the flavour of H.

Placebo expectancy effects in the relationship between glucose and cognition.

The present study investigated the extent of expectancy in the ability of glucose to affect cognitive performance. Using a within-subjects design, subjects (n 26) completed four experimental sessions (in counterbalanced order and after an initial practice session) during which they were given a 500 ml drink 30 min prior to completing a cognitive assessment battery. In addition, all subjects completed a baseline practice session during which they were given no drink. During two of the sessions, subjects were given a drink containing 50 g glucose and on the other two they were given a drink containing aspartame. A balanced placebo design was used, such that for half the sessions subjects were accurately informed as to the content of the drink (glucose or aspartame), whereas in the other two sessions they were misinformed as to the content of the drink. The task battery comprised a 6 min visual analogue of the Bakan vigilance task, an immediate verbal free-recall task, an immediate verbal recognition memory task and a measure of motor speed (two-finger tapping). Blood glucose and self-reported mood were also recorded at several time points during each session. Glucose administration was found to improve recognition memory times, in direct contrast to previous findings in the literature. Glucose administration also improved performance on the Bakan task (relative to the control drink), but only in sessions where subjects were informed that they would receive glucose and not when they were told that they would receive aspartame. There were no effects either of the nature of the drink or expectancy on the other measures. These results are interpreted in terms of there being some contribution of expectancy concerning the positive effects of glucose on cognition in studies which have not used an equi-sweet dose of aspartame as a control drink.

Dietary restraint and addictive behaviors: the generalizability of Tiffany's cue reactivity model.

UNLABELLED: Two studies are presented, which examine cue reactivity in dieting. METHODS: Experiment 1 investigated whether the presence of a preferred food affected dieters' performance on measures of attention, reaction time, and motor speed. The manipulation did not affect the performance. Experiment 2 investigated the performance of dieters (N = 19), highly restrained non-dieters (N = 18) and low-to-medium restrained eaters (N = 34) on two simple reaction time tasks. Subjects were either required to imagine their favorite food or to imagine their favorite holiday while completing a reaction time task. RESULTS: In the food condition, both dieters and restrained nondieters displayed significantly slower reaction times during the first three of five blocks of the task than the low-to-medium restrained eaters. CONCLUSIONS: The results are discussed in terms of Tiffany's (Psychological Review 97:147-168, 1990) model of cue reactivity in that different abstinent states produce comparable effects upon performance.

An investigation of satiety in ageing, dementia, and hyperphagia.

OBJECTIVE: To investigate satiety in young, middle-aged, and elderly healthy adults, and in nonhyperphagic and hyperphagic elderly people with dementia. Previous work suggested hyperphagia in dementia was due to increased hunger and absence of satiation. METHODS: The primary measure of satiety was the amount of food eaten in an ad libitum meal, given 1 hr after a fixed preload. Three types of preload were used, high- and low-energy milkshakes and water. The effect of age was investigated by comparing the three groups of healthy adults. The effect of dementia was investigated by comparing the two demented groups with healthy elderly. RESULTS: Measurements suggested that accuracy of compensation for preload energy differences decreased with age and was absent in people with dementia. DISCUSSION: Lack of compensatory response in the elderly, particularly those with dementia, indicates the need for monitoring food intake to prevent over- or undereating.

Gender differences in colour naming performance for gender specific body shape images.

Males are increasingly subjected to pressures to conform to aesthetic body stereotypes. There is, however, comparatively little published research on the aetiology of male body shape concerns. Two experiments are presented, which investigate the relationship between gender specific body shape concerns and colour-naming performance. Each study comprised a between subject design, in which each subject was tested on a single occasion. A pictorial version of a modified Stroop task was used in both studies. Subjects colour-named gender specific obese and thin body shape images and semantically homogeneous neutral images (birds) presented in a blocked format. The first experiment investigated female subjects (N = 68) and the second investigated males (N = 56). Subjects also completed a self-report measure of eating behaviour. Currently dieting female subjects exhibited significant colour-naming differences between obese and neutral images. A similar pattern of colour-naming performance was found to be related to external eating in the male subjects.

The effects of food deprivation and incentive motivation on blood glucose levels and cognitive function.

The current study investigated the relationships between blood glucose levels, mild food deprivation, sympathetic arousal, and cognitive processing efficiency. Subjects (n = 82) were randomly assigned to four experimental conditions, comprising combined manipulations of food deprivation and incentive motivation. Baseline and mid-session measurements of blood glucose, blood pressure and pulse rate were taken. Subjects completed a number of measures of cognitive processing efficiency and self report measures of affective and somatic state. Although glucose levels were lowered following food deprivation, there was no significant detrimental effect of food deprivation on task performance. However, improved recognition memory processing times were associated with deprivation. Incentive motivation was associated with faster simple reaction times and higher diastolic blood pressure. There were no significant relationships between glucose levels and task performance, further supporting the hypothesis that the brain is relatively invulnerable to short food deprivation.

Cognitive effects of a long-term weight reducing diet.

OBJECTIVE: To investigate if long-term caloric restriction under controlled conditions adversely affects cognitive function in obese women. SUBJECTS: Healthy, premenopausal women between 23-42 y. Dieting group: n = 14. CONTROL GROUP: n = 11. DESIGN: Longitudinal weight loss study (repeated measures within-subject design) with 3 weeks of baseline, 15 weeks of 50% caloric restriction, and 3 weeks of weight stabilization. MEASUREMENTS: Computerized cognitive function tests (sustained attention, short-term memory, simple reaction time, motor performance and attentional focus), height, body weight, body composition (TOBEC) and behavioral questionnaires (Dutch Eating Behaviour Questionnaire, Eating Attitudes Test, and State-Trait Anxiety Inventory). RESULTS: Dieting women lost 12.3 +/- 5.5 kg (mean +/- s.d.) of body weight. Controlled long-term caloric restriction significantly slowed simple reaction time but did not diminish sustained attention, motor performance or immediate memory. Word recall performance significantly improved by 24% at the end of caloric restriction. CONCLUSIONS: The slowing of simple reaction time is a short-term and long-term consequence of caloric restriction. In contrast to previous short-term dieting studies, sustained attention and immediate memory were not impaired with long-term caloric restriction.

Impaired color naming of food and body shape words: weight phobia or distinct affective state?

OBJECTIVE: The current study investigated whether a concern with body shape and weight represents a distinct affective state, or whether it is better conceptualized as a highly specific form of anxiety. METHOD: The color-naming performance of women with a high Drive for Thinness score was examined under three experimental conditions: when a photograph of chocolate was present, when actual chocolate was present, and a control condition. High Drive for Thinness subjects demonstrated relatively impaired color naming of body shape words in the picture condition, but not in the food or control conditions. RESULTS: Although there was a significant impairment in the color naming of food words, this was unaffected by condition or degree of Drive for Thinness. DISCUSSION: The results are interpreted as supporting an analogy between weight/body shape concerns and subclinical phobic anxiety.

Cognitive functioning, weight change and therapy in anorexia nervosa.

Anorexia nervosa is associated with impairments in cognitive function which have been hypothesized to be fundamentally attentional in nature. The current study investigated whether therapy and weight gain affect these impairments. A group of anorexics (N = 12) completed a battery of cognitive performance tasks and self-report measures of psychopathology on three occasions, over the course of 12 weeks of in-patient treatment. A non-clinical control population (N = 17) completed the same measures. The anorexics improved on all measures of psychopathology and affective state as a result of therapy. Anorexics displayed poorer recall, reaction times, and motor speed than the control subjects. Although there was a gain in weight over the course of therapy, there was no corresponding improvement in cognitive performance. Impaired task performance in anorexics was not directly related to their psychopathology or affective state.

Conditioned flavour preferences reinforced by caffeine consumed after lunch.

Caffeine-consuming adult males and females were divided into two groups, those who regularly consumed a caffeinated drink after lunch ("users" n = 21) and those who did not ("nonusers" n = 23). After lunch on weekdays during a 2-week conditioning period, these subjects consumed a novel flavoured fruit juice drink paired with either a caffeine (100 mg) or a placebo capsule. Preferences for this "target" drink and six other novel-flavoured fruit juice drinks were assessed before and then after 5 and 10 conditioning trials. The users showed a significantly greater increase in preference for the caffeine-paired target drink than for the placebo-paired target drink, whereas the nonusers showed a slight trend in the opposite direction. These changes in preference did not generalise to the nontarget drink flavours. For habitual postlunch caffeine users, caffeine alleviated the postlunch dip in mood experienced by those in the placebo condition. Thus, the increase in preference for the caffeine-paired target drink was consistent with the improved mood state that resulted from caffeine consumption. It is unlikely, however, that the subjects were aware of this relationship. These results provide strong evidence for the existence of a reinforcing effect of caffeine, which probably plays a significant role in the acquisition of preferences for caffeine-containing drinks.

Hunger, caloric preloading and the selective processing of food and body shape words.

Fifty-three female subjects performed a modified Stroop colour-naming task 30 minutes after consuming a high-calorie preload, a low-calorie preload or water. Half of the subjects were 18 hours food deprived prior to testing. Food restriction and the caloric density of the preload had no effect on the colour-naming of food-related words. However, impairments in the colour-naming of food-related words did vary according to the subjects' self-reported hunger level. This relationship between hunger and colour-naming impairment was not linear, with the most hungry subjects displaying the smallest impairment in the colour naming of food words. The results are interpreted in terms of recent thought on the relationship between attentional processing and fear arousal.

Mood and performance effects of caffeine in relation to acute and chronic caffeine deprivation.

The mood and performance effects of caffeine deprivation (either 90 min, overnight, or at least 7 days) and ingestion (70 and 250 mg) were compared in young adults who were normally either moderate consumers (n = 49) or nonconsumers of caffeine (n = 18). Overnight caffeine deprivation produced dysphoric symptoms characteristic of caffeine withdrawal that were reduced, but still present, after longer-term abstinence. Acute caffeine intake affected the withdrawn consumers, nonwithdrawn consumers, and nonconsumers similarly. It increased jitteriness and decrease tiredness and headache. Furthermore, hand steadiness decreased as caffeine dose increased, whereas 70 mg, but not 250 mg, of caffeine was found to enhance performance on a simple reaction time task. These findings support the view that the negative effects experienced after overnight and longer-term caffeine deprivation play a significant role in influencing consumption of caffeine-containing drinks. Therefore, it would appear that to avoid the dysphoric symptoms resulting from both under- and overconsumption, regular caffeine consumers would have to regulate their caffeine intake fairly precisely.

Overnight caffeine abstinence and negative reinforcement of preference for caffeine-containing drinks.

It has been suggested that liking for the taste, flavour and aroma of, for example, coffee and tea is acquired through the process of classical conditioning, involving association of these orosensory cues with the psychopharmacological consequences of caffeine ingestion. Accordingly, this study investigated caffeine reinforcement by assessing changes in preference for a novel drink consumed with or without caffeine. Particular care was taken to use "ecologically valid" procedures; that is, overnight caffeine abstinence followed by a cup-of-coffee equivalent dose of caffeine (70 mg) at breakfast. Caffeine had no significant effects on drink preference or mood in subjects with habitually low intakes of caffeine. In contrast, moderate users of caffeine developed a relative dislike for the drink lacking caffeine and showed somewhat lowered mood following overnight caffeine abstinence (e.g., less lively, clearheaded and cheerful), which was significantly improved by caffeine. These together with other recent results strongly suggest that, in everyday life, caffeine reinforcement can occur as the result of the alleviation by caffeine of the adverse effects of overnight caffeine abstinence (negative reinforcement). They also demonstrate the utility of this flavour-conditioning procedure, which could be applied in the wider investigation of the reinforcing properties of drugs.

Lack of effect of short-term fasting on cognitive function.

In a study designed to assess the effects of short-term food deprivation on cognitive function, a sample of female subjects (N = 21) was tested on a number of measures of cognitive function after three levels of food deprivation (miss one meal, miss two meals or miss all food for 24 h prior to testing) and a condition in which they ate normally for 24 h prior to testing. There was found to be no significant effects of food deprivation on sustained attention, attentional focus, simple reaction time or immediate memory. However, performance on a low processing load tapping task was significantly poorer when the subjects were deprived of food for 24 h prior to testing, and heart rate was significantly higher when they were non-deprived. These results stand in contrast to the impairments in cognitive function previously found to be associated with spontaneous dieting behaviour (using essentially the same task battery).

Impairment of cognitive performance associated with dieting and high levels of dietary restraint.

Seventy women students were tested on a short battery of tasks assessing cognitive performance. They also completed self-report ratings of mood, the Dutch Eating Behaviour Questionnaire (DEBQ) to which was appended several additional items concerning their recent dieting behaviour, and a 24-h dietary recall. Heart rate was measured before and after testing. Compared with nondieting subjects with low to moderate scores on the restraint factor of the DEBQ, subjects (n = 15) who reported that they were currently dieting to lose weight displayed impaired performance on a vigilance task and also tended to show poorer immediate memory and longer reaction times. Highly restrained eaters who were not dieting at the time of testing, on the whole, performed at an intermediate level on these tests. In contrast, the dieters tended to show the best performance on an undemanding finger tapping task, indicating that they were not slowed in their fine motor responses or lacking in motivation to carry out the tasks. Poorer cognitive functioning during dieting could arise as a direct consequence of the effects of food restriction on energy metabolism or other physiological mechanisms--the dietary records indicated that the current dieters were eating at about 70% of maintenance energy requirement. However, it is also possible that cognitive performance is impaired during dieting due to anxiety resulting from stressful effects of imposing and maintaining dietary restraint.

Current attitudes and future influences on meat consumption in the U.K.

A survey of 1018 U.K. residents was conducted using the basic structure of the theory of reasoned action along with scenarios of possible future events investigating meat-eating and vegetarianism. Over a quarter (28%) of the sample considered themselves to be reducing meat consumption although a comparison of present and retrospective meat consumption indicated that less than a quarter of this group had cut down on a variety of meats in their diets over the past year. The attitudes related to present meat consumption were healthiness, taste, value for money and, to some extent, ethical issues. Healthiness, taste and concerns over additives were related to changes in meat consumption over the preceding year. Beliefs about the healthiness of meat were also related to reported changes in meat-eating behaviour when "something that could possibly happen in the future" was described. Future events found to affect people's estimated meat-eating were the availability of polyunsaturated meat and meat produced with strict safety guarantees, the former change being dependent on a constant price. Reductions in the fat content of meat or claims extolling the nutritional benefits of eating meat were not related to predicted future meat-eating.