Systematic review and individual patient data meta-analysis of diagnosis of heart failure, with modelling of implications of different diagnostic strategies in primary care

OBJECTIVES

To assess the accuracy in diagnosing heart failure of clinical features and potential primary care investigations, and to perform a decision analysis to test the impact of plausible diagnostic strategies on costs and diagnostic yield in the UK health-care setting.

DATA SOURCES

MEDLINE and CINAHL were searched from inception to 7 July 2006. 'Grey literature' databases and conference proceedings were searched and authors of relevant studies contacted for data that could not be extracted from the published papers.

REVIEW METHODS

A systematic review of the clinical evidence was carried out according to standard methods. Individual patient data (IPD) analysis was performed on nine studies, and a logistic regression model to predict heart failure was developed on one of the data sets and validated on the other data sets. Cost-effectiveness modelling was based on a decision tree that compared different plausible investigation strategies.

RESULTS

Dyspnoea was the only symptom or sign with high sensitivity (89%), but it had poor specificity (51%). Clinical features with relatively high specificity included history of myocardial infarction (89%), orthopnoea (89%), oedema (72%), elevated jugular venous pressure (70%), cardiomegaly (85%), added heart sounds (99%), lung crepitations (81%) and hepatomegaly (97%). However, the sensitivity of these features was low, ranging from 11% (added heart sounds) to 53% (oedema). Electrocardiography (ECG), B-type natriuretic peptides (BNP) and N-terminal pro-B-type natriuretic peptides (NT-proBNP) all had high sensitivities (89%, 93% and 93% respectively). Chest X-ray was moderately specific (76-83%) but insensitive (67-68%). BNP was more accurate than ECG, with a relative diagnostic odds ratio of ECG/BNP of 0.32 (95% CI 0.12-0.87). There was no difference between the diagnostic accuracy of BNP and NT-proBNP. A model based upon simple clinical features and BNP derived from one data set was found to have good validity when applied to other data sets. A model substituting ECG for BNP was less predictive. From this a simple clinical rule was developed: in a patient presenting with symptoms such as breathlessness in whom heart failure is suspected, refer directly to echocardiography if the patient has a history of myocardial infarction or basal crepitations or is a male with ankle oedema; otherwise, carry out a BNP test and refer for echocardiography depending on the results of the test. On the basis of the cost-effectiveness analysis carried out, such a decision rule is likely to be considered cost-effective to the NHS in terms of cost per additional case detected. The cost-effectiveness analysis further suggested that, if likely benefit to the patient in terms of improved life expectancy is taken into account, the optimum strategy would be to refer all patients with symptoms suggestive of heart failure directly for echocardiography.

CONCLUSIONS

The analysis suggests the need for important changes to the NICE recommendations. First, BNP (or NT-proBNP) should be recommended over ECG and, second, some patients should be referred straight for echocardiography without undergoing any preliminary investigation. Future work should include evaluation of the clinical rule described above in clinical practice.

The Short-Form Leeds Dyspepsia Questionnaire validation study

BACKGROUND

Assessment of symptoms should be the primary outcome measure in dyspepsia clinical trials. This requires a reliable, valid and responsive questionnaire that measures the frequency and severity of dyspepsia. The Leeds Dyspepsia Questionnaire fulfils these characteristics, but is long and was not designed for self-completion, so a shorter questionnaire was developed (the Short-Form Leeds Dyspepsia Questionnaire).

AIM

To assess the acceptability, interpretability, internal consistency, reliability, validity and responsiveness of the Short-Form Leeds Dyspepsia Questionnaire in primary and secondary care.

METHODS

Unselected primary and secondary care patients completed the Short-Form Leeds Dyspepsia Questionnaire. Test-retest reliability was assessed after 2 days. Validity was measured by comparison with general practitioners' diagnosis. Sensitivity analysis and logistic regression were employed to determine the most valid scoring system. Responsiveness was determined before and after treatment for endoscopically proven disease.

RESULTS

The Short-Form Leeds Dyspepsia Questionnaire was administered to 388 primary care and 204 secondary care patients. The Pearson coefficient for test-retest reliability was 0.93. The Short-Form Leeds Dyspepsia Questionnaire had a sensitivity of 77% and a specificity of 75%. A highly significant response to change was observed (P < 0.005).

CONCLUSIONS

The Short-Form Leeds Dyspepsia Questionnaire is a reliable, valid and responsive self-completed outcome measure for quantifying the frequency and severity of dyspepsia symptoms, which is shorter and more convenient than the Leeds Dyspepsia Questionnaire.

Initial management strategies for dyspepsia

BACKGROUND

This review considers management strategies (combinations of initial investigation and empirical treatments) for dyspeptic patients. Dyspepsia was defined to include both epigastric pain and heartburn.

OBJECTIVES

To determine the effectiveness, acceptability, and cost effectiveness of the following initial management strategies for patients presenting with dyspepsia: (a) Initial pharmacological therapy (including endoscopy for treatment failures). (b) Early endoscopy. (c) Testing for Helicobacter pylori (H. pylori )and endoscope only those positive. (d) H. pylori eradication therapy with or without prior testing.

SEARCH STRATEGY

Trials were located through electronic searches and extensive contact with trialists.

SELECTION CRITERIA

All randomised controlled trials of dyspeptic patients presenting in primary care.

DATA COLLECTION AND ANALYSIS

Data were collected on dyspeptic symptoms, quality of life and use of resources. An individual patient data meta-analysis of health economic data was conducted

MAIN RESULTS

Twenty-five papers reporting 27 comparisons were found. Trials comparing proton pump inhibitors (PPI) with antacids (three trials) and histamine H2-receptor antagonists (H2RAs) (three trials), early endoscopy with initial acid suppression (five trials), H. pylori test and endoscope versus usual management (three trials), H. pylori test and treat versus endoscopy (six trials), and test and treat versus acid suppression alone in H. pylori positive patients (four trials), were pooled. PPIs were significantly more effective than both H2RAs and antacids. Relative risks (RR) and 95% confidence intervals (CI) were; for PPI compared with antacid 0.72 (95% CI 0.64 to 0.80), PPI compared with H2RA 0.63 (95% CI 0.47 to 0.85). Results for other drug comparisons were either absent or inconclusive. Initial endoscopy was associated with a small reduction in the risk of recurrent dyspeptic symptoms compared with H. pylori test and treat (OR 0.75, 95% CI 0.58 to 0.96), but was not cost effective (mean additional cost of endoscopy US$401 (95% CI $328 to 474). Test and treat may be more effective than acid suppression alone (RR 0.59 95% CI 0.42 to 0.83).

AUTHORS' CONCLUSIONS

Proton pump inhibitor drugs (PPIs) are effective in the treatment of dyspepsia in these trials which may not adequately exclude patients with gastro-oesophageal reflux disease (GORD). The relative efficacy of histamine H2-receptor antagonists (H2RAs) and PPIs is uncertain. Early investigation by endoscopy or H. pylori testing may benefit some patients with dyspepsia but is not cost effective as part of an overall management strategy.

Effect of chronic treatment with the GABA transaminase inhibitors gamma-vinyl GABA and ethanolamine O-sulphate on the in vitro GABA release from rat hippocampus

1. The effects of 2, 8 and 21 day oral treatment with the specific gamma-aminobutyric acid transaminase (GABA-T) inhibitors gamma-vinyl GABA (GVG) and ethanolamine O-sulphate (EOS) on brain GABA levels, GABA-T activity, and basal and stimulated GABA release from rat cross-chopped brain hippocampal slices was investigated. 2. Treatment with GABA-T inhibitors lead to a reduction in brain GABA-T activity by 65-80% compared with control values, with a concomitant increase in brain GABA content of 40-100%. 3. Basal hippocampal GABA release was increased to 250-450% of control levels following inhibition of GABA-T activity. No Ca2+ dependence was observed in either control or treated tissues. 4. GVG and EOS administration led to a significant elevation in the potassium stimulated release of GABA from cross-chopped hippocampal slices compared with that of controls. Although stimulated GABA release from control tissues was decreased in the presence of a low Ca2+ medium, GVG and EOS treatment abolished this Ca2+ dependency. 5. GABA compartmentalization, Na+ and Cl- coupled GABA uptake carriers and glial release may provide explanations for the loss of the Ca2+ dependency of stimulated GABA release observed following GVG and EOS treatment. 6. Administration of GABA-T inhibitors led to increases in both basal and stimulated hippocampal GABA release. However, it is not clear which is the most important factor in the anticonvulsant activity of these drugs, the increased GABA content 'leaking' out of neurones and glia leading to widespread inhibition, or the increase in stimulated GABA release which may occur following depolarization caused by an epileptic discharge.

Effects of chronic oral treatment with GABA-transaminase inhibitors on the GABA system in brain, liver, kidney, and plasma of the rat

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is not solely located in the CNS, it and the enzymes responsible for its synthesis (glutamic acid decarboxylase, GAD, EC 4.1.1.15) and catabolism (GABA-transaminase, GABA-T, EC 2.6.1.19) are also present in non-neuronal organs. Following 2, 8 and 21 day oral administration of ethanolamine-O-sulphate (EOS) and gamma-vinyl GABA (GVG), two irreversible inhibitors of GABA-T, the GABA content and activities of GAD and GABA-T in rat brain, liver and kidney, and the GABA content of plasma were determined: GABA-T activity was significantly decreased (over 80%) in liver, brain and kidney, although there was 2-3 times the residual activity left in the brain compared with the peripheral organs. GABA content was subsequently significantly elevated in the liver (300-1500%), plasma (200-300%) and brain (200-300%), although, surprisingly, the kidney GABA content was reduced (by 60-70%) compared with control. GAD activity was decreased following 8 day treatment in liver and brain. Kidney GAD was reduced at all time points. These two compounds are anticonvulsant, GVG is used clinically for the treatment of epilepsy but it seems that these drugs have significant peripheral effects.

The effect of chronic treatment with the GABA transaminase inhibitors gamma-vinyl-GABA and ethanolamine-O-sulphate on the in vivo release of GABA from rat hippocampus

The effects of chronic treatment with the specific, mechanism-based, irreversible inhibitors of 4-aminobutyrate aminotransferase (EC 2.6.1.19; GABA transaminase), ethanolamine O-sulphate (EOS), and 4-aminohexenoate [vigabatrin; gamma-vinyl-GABA (GVG)] on the extracellular concentrations of GABA in the hippocampus have been studied using in vivo microdialysis in conscious animals. Oral dosing [3 mg/ml of drinking water, giving doses of GVG of 194 +/- 38 mg/kg/day and of EOS of 303 +/- 42 mg/kg/day (mean +/- SD)] was followed by microdialysis at 2, 8, and 21 days. The basal outflow of GABA (in the range of approximately 1-2 pmol/30 microliters/30-min sample) after 2 and 8 days of treatment was not significantly different from that in control animals, but the 21-day treatment gave significant rises in the extracellular GABA concentration (up to approximately 6-8 pmol/30 microliters/30-min sample). Both inhibitors gave similar results. Depolarisation with 100 mM K+ gave large increases in GABA release in control (approximately 20-60 pmol/30 microliters/30-min sample) and treated animals. The 8- and 21-day-treated animals showed significant increases in the stimulated release compared with control animals (approximately 80-100 pmol/30 microliters/30-min sample). Excluding Ca2+ had no significant effect on either basal or stimulated release. The significant increases in K(+)-evoked release of GABA show that the increased intracellular pool of GABA is available for release, and this may be related to the anticonvulsant action of these compounds.

beta-Amyloid precursor protein isoforms show correlations with neurones but not with glia of demented subjects

Post-mortem cerebral cortex from 15 demented patients was specially collected to minimise autolysis and two membrane fractions and one soluble fraction were quantitatively examined for the major species of beta-amyloid precursor protein (APP) of high apparent molecular mass (> or = 80 kDa) together with the major mRNA species encoding APP isoforms. The number of pyramidal neurones and astrocytes, putative biochemical indices of interneurones and pyramidal neurones, and choline acetyl transferase activity were also determined. Multiple regression analysis has been used to investigate intercorrelations of APP species with biochemical and morphometric measures, free of any effects of confounding demographic variables. Subjects with Alzheimer's disease showed a loss of cholinergic activity and D-aspartate uptake compared with patients with other causes of dementia. The major finding of the study is that measures of neurones rather than astrocytes most closely correlate with the concentration of APP. Pyramidal cell numbers were positively correlated with mRNA for APP695. APP in the soluble fraction showed a negative correlation with pyramidal cell numbers and cholinergic activity. These results indicate that neurones within the cerebral cortex are the major source of APP, and that secretion of APP is dependent upon cortical pyramidal neuronal activity and cholinergic activity.

Pharmacological characterisation of excitatory synaptic transmission in the cat red nucleus in vivo

Extracellular recordings were made from the magnocellular neurones of the red nucleus (mRN) in anaesthetised cats. A study was made of the effects of selective excitatory amino acid receptor antagonists on excitatory monosynaptic responses evoked from the sensorimotor cortex (SMC) and cerebellar interpositus nucleus (IPN). Iontophoretically applied CNQX and NBQX antagonised both SMC and IPN responses whereas, D-AP5 inhibited the SMC response but was ineffective to the IPN. At currents that selectively antagonised NMDA responses, CPPene had no effect on either SMC or IPN responses. 7-chlorokynurenate inhibited both SMC and IPN responses but required currents that antagonised both AMPA and NMDA responses and was therefore acting in a non-selective manner. Iontophoretically applied glycine was inhibitory to both agonist and synaptic responses, whilst D-serine potentiated NMDA responses but did not enhance monosynaptic responses of the SMC. However in the presence of either 7-chlorokynurenate or high currents of CNQX that reduced the SMC synaptic activation of the mRN neurones, D-serine attenuated the inhibitory action of these antagonists. It is concluded that monosynaptic responses from the SMC are mediated by both NMDA and non-NMDA receptors whereas the monosynaptic responses evoked from the IPN are mediated only by non-NMDA receptors. The lack of effect of CPPene is consistent with the postulate that two NMDA receptor subtypes are present on mRN neurones.