Quality of MALDI-TOF mass spectra in routine diagnostics: results from an international external quality assessment including 36 laboratories from 12 countries using 47 challenging bacterial strains.

OBJECTIVES: Matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) is a widely used method for bacterial species identification. Incomplete databases and mass spectral quality (MSQ) still represent major challenges. Important proxies for MSQ are the number of detected marker masses, reproducibility, and measurement precision. We aimed to assess MSQs across diagnostic laboratories and the potential of simple workflow adaptations to improve it. METHODS: For baseline MSQ assessment, 47 diverse bacterial strains, which are challenging to identify by MALDI-TOF MS, were routinely measured in 36 laboratories from 12 countries, and well-defined MSQ features were used. After an intervention consisting of detailed reported feedback and instructions on how to acquire MALDI-TOF mass spectra, measurements were repeated and MSQs were compared. RESULTS: At baseline, we observed heterogeneous MSQ between the devices, considering the median number of marker masses detected (range = [2-25]), reproducibility between technical replicates (range = [55%-86%]), and measurement error (range = [147 parts per million (ppm)-588 ppm]). As a general trend, the spectral quality was improved after the intervention for devices, which yielded low MSQs in the baseline assessment as follows: for four out of five devices with a high measurement error, the measurement precision was improved (p-values <0.001, paired Wilcoxon test); for six out of ten devices, which detected a low number of marker masses, the number of detected marker masses increased (p-values <0.001, paired Wilcoxon test). DISCUSSION: We have identified simple workflow adaptations, which, to some extent, improve MSQ of poorly performing devices and should be considered by laboratories yielding a low MSQ. Improving MALDI-TOF MSQ in routine diagnostics is essential for increasing the resolution of bacterial identification by MALDI-TOF MS, which is dependent on the reproducible detection of marker masses. The heterogeneity identified in this external quality assessment (EQA) requires further study.

C-reactive protein point-of-care testing for safely reducing antibiotics for acute exacerbations of chronic obstructive pulmonary disease: the PACE RCT.

BACKGROUND: Most patients presenting with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in primary care are prescribed antibiotics, but these may not be beneficial, and they can cause side effects and increase the risk of subsequent resistant infections. Point-of-care tests (POCTs) could safely reduce inappropriate antibiotic prescribing and antimicrobial resistance. OBJECTIVE: To determine whether or not the use of a C-reactive protein (CRP) POCT to guide prescribing decisions for AECOPD reduces antibiotic consumption without having a negative impact on chronic obstructive pulmonary disease (COPD) health status and is cost-effective. DESIGN: A multicentre, parallel-arm, randomised controlled open trial with an embedded process, and a health economic evaluation. SETTING: General practices in Wales and England. A UK NHS perspective was used for the economic analysis. PARTICIPANTS: Adults (aged ≥ 40 years) with a primary care diagnosis of COPD, presenting with an AECOPD (with at least one of increased dyspnoea, increased sputum volume and increased sputum purulence) of between 24 hours' and 21 days' duration. INTERVENTION: CRP POCTs to guide antibiotic prescribing decisions for AECOPD, compared with usual care (no CRP POCT), using remote online randomisation. MAIN OUTCOME MEASURES: Patient-reported antibiotic consumption for AECOPD within 4 weeks post randomisation and COPD health status as measured with the Clinical COPD Questionnaire (CCQ) at 2 weeks. For the economic evaluation, patient-reported resource use and the EuroQol-5 Dimensions were included. RESULTS: In total, 653 participants were randomised from 86 general practices. Three withdrew consent and one was randomised in error, leaving 324 participants in the usual-care arm and 325 participants in the CRP POCT arm. Antibiotics were consumed for AECOPD by 212 out of 274 participants (77.4%) and 150 out of 263 participants (57.0%) in the usual-care and CRP POCT arm, respectively [adjusted odds ratio 0.31, 95% confidence interval (CI) 0.20 to 0.47]. The CCQ analysis comprised 282 and 281 participants in the usual-care and CRP POCT arms, respectively, and the adjusted mean CCQ score difference at 2 weeks was 0.19 points (two-sided 90% CI -0.33 to -0.05 points). The upper limit of the CI did not contain the prespecified non-inferiority margin of 0.3. The total cost from a NHS perspective at 4 weeks was £17.59 per patient higher in the CRP POCT arm (95% CI -£34.80 to £69.98; p = 0.408). The mean incremental cost-effectiveness ratios were £222 per 1% reduction in antibiotic consumption compared with usual care at 4 weeks and £15,251 per quality-adjusted life-year gained at 6 months with no significant changes in sensitivity analyses. Patients and clinicians were generally supportive of including CRP POCT in the assessment of AECOPD. CONCLUSIONS: A CRP POCT diagnostic strategy achieved meaningful reductions in patient-reported antibiotic consumption without impairing COPD health status or increasing costs. There were no associated harms and both patients and clinicians valued the diagnostic strategy. FUTURE WORK: Implementation studies that also build on our qualitative findings could help determine the effect of this intervention over the longer term. TRIAL REGISTRATION: Current Controlled Trials ISRCTN24346473. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 15. See the NIHR Journals Library website for further project information.

People with chronic obstructive pulmonary disease (COPD) often experience flare-ups known as acute exacerbations of chronic obstructive pulmonary disease. Antibiotics are prescribed for most flare-ups, but they do not always benefit patients and may cause harm, such as side effects or subsequent infections that are resistant. Rapid point-of-care tests (POCTs) can be used to help determine when antibiotics are more likely to be needed. C-reactive protein (CRP) is a marker of inflammation that can be measured with a POCT. Patients with flare-ups and a low CRP value are less likely to benefit from antibiotics. The PACE trial asked whether or not measuring CRP with a POCT could lead to fewer antibiotics being consumed for flare-ups, without having negative effects for patients. We aimed to recruit 650 patients with a COPD flare-up from primary care. Patients were randomly assigned to either (1) usual care with the addition of a CRP POCT, or (2) usual care without the addition of the test. Antibiotic use over the first 4 weeks and patients' self-assessment of their health 2 weeks after enrolment were measured in both groups. Patients in the CRP test group used fewer antibiotics than those managed as usual, and had improved patient-reported outcomes. Costs were a little higher in the CRP POCT group. Interviews with patients and clinicians found that they appreciated the CRP test being included in the decision-making process.

C-Reactive Protein Testing to Guide Antibiotic Prescribing for COPD Exacerbations.

BACKGROUND: Point-of-care testing of C-reactive protein (CRP) may be a way to reduce unnecessary use of antibiotics without harming patients who have acute exacerbations of chronic obstructive pulmonary disease (COPD). METHODS: We performed a multicenter, open-label, randomized, controlled trial involving patients with a diagnosis of COPD in their primary care clinical record who consulted a clinician at 1 of 86 general medical practices in England and Wales for an acute exacerbation of COPD. The patients were assigned to receive usual care guided by CRP point-of-care testing (CRP-guided group) or usual care alone (usual-care group). The primary outcomes were patient-reported use of antibiotics for acute exacerbations of COPD within 4 weeks after randomization (to show superiority) and COPD-related health status at 2 weeks after randomization, as measured by the Clinical COPD Questionnaire, a 10-item scale with scores ranging from 0 (very good COPD health status) to 6 (extremely poor COPD health status) (to show noninferiority). RESULTS: A total of 653 patients underwent randomization. Fewer patients in the CRP-guided group reported antibiotic use than in the usual-care group (57.0% vs. 77.4%; adjusted odds ratio, 0.31; 95% confidence interval [CI], 0.20 to 0.47). The adjusted mean difference in the total score on the Clinical COPD Questionnaire at 2 weeks was -0.19 points (two-sided 90% CI, -0.33 to -0.05) in favor of the CRP-guided group. The antibiotic prescribing decisions made by clinicians at the initial consultation were ascertained for all but 1 patient, and antibiotic prescriptions issued over the first 4 weeks of follow-up were ascertained for 96.9% of the patients. A lower percentage of patients in the CRP-guided group than in the usual-care group received an antibiotic prescription at the initial consultation (47.7% vs. 69.7%, for a difference of 22.0 percentage points; adjusted odds ratio, 0.31; 95% CI, 0.21 to 0.45) and during the first 4 weeks of follow-up (59.1% vs. 79.7%, for a difference of 20.6 percentage points; adjusted odds ratio, 0.30; 95% CI, 0.20 to 0.46). Two patients in the usual-care group died within 4 weeks after randomization from causes considered by the investigators to be unrelated to trial participation. CONCLUSIONS: CRP-guided prescribing of antibiotics for exacerbations of COPD in primary care clinics resulted in a lower percentage of patients who reported antibiotic use and who received antibiotic prescriptions from clinicians, with no evidence of harm. (Funded by the National Institute for Health Research Health Technology Assessment Program; PACE Current Controlled Trials number, ISRCTN24346473.).

Point-of-care urine culture for managing urinary tract infection in primary care: a randomised controlled trial of clinical and cost-effectiveness.

BACKGROUND: The effectiveness of using point-of-care (POC) urine culture in primary care on appropriate antibiotic use is unknown. AIM: To assess whether use of the Flexicult™ SSI-Urinary Kit, which quantifies bacterial growth and determines antibiotic susceptibility at the point of care, achieves antibiotic use that is more often concordant with laboratory culture results, when compared with standard care. DESIGN AND SETTING: Individually randomised trial of females with uncomplicated urinary tract infection (UTI) in primary care research networks (PCRNs) in England, the Netherlands, Spain, and Wales. METHOD: Multilevel regression compared outcomes between the two groups while controlling for clustering. RESULTS: In total, 329 participants were randomised to POC testing (POCT) and 325 to standard care, and 324 and 319 analysed. Fewer females randomised to the POCT arm than those who received standard care were prescribed antibiotics at the initial consultation (267/324 [82.4%] versus 282/319 [88.4%], odds ratio [OR] 0.56, 95% confidence interval [CI] = 0.35 to 0.88). Clinicians indicated the POCT result changed their management for 190/301 (63.1%). Despite this, there was no statistically significant difference between study arms in antibiotic use that was concordant with laboratory culture results (primary outcome) at day 3 (39.3% POCT versus 44.1% standard care, OR 0.84, 95% CI = 0.58 to 1.20), and there was no evidence of any differences in recovery, patient enablement, UTI recurrences, re-consultation, antibiotic resistance, and hospitalisations at follow-up. POCT culture was not cost-effective. CONCLUSION: Point-of-care urine culture was not effective when used mainly to adjust immediate antibiotic prescriptions. Further research should evaluate use of the test to guide initiation of 'delayed antibiotics'.

General practitioner use of a C-reactive protein point-of-care test to help target antibiotic prescribing in patients with acute exacerbations of chronic obstructive pulmonary disease (the PACE study): study protocol for a randomised controlled trial.

BACKGROUND: Most patients presenting with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in primary care are prescribed an antibiotic, which may not always be appropriate and may cause harm. C-reactive protein (CRP) is an acute-phase biomarker that can be rapidly measured at the point of care and may predict benefit from antibiotic treatment in AECOPD. It is not clear whether the addition of a CRP point-of-care test (POCT) to clinical assessment leads to a reduction in antibiotic consumption without having a negative impact on COPD health status. METHODS/DESIGN: This is a multicentre, individually randomised controlled trial (RCT) aiming to include 650 participants with a diagnosis of AECOPD in primary care. Participants will be randomised to be managed according to usual care (control) or with the addition of a CRP POCT to guide antibiotic prescribing. Antibiotic consumption for AECOPD within 4 weeks post randomisation and COPD health status (total score) measured by the Clinical COPD Questionnaire (CCQ) at 2 weeks post randomisation will be co-primary outcomes. Primary analysis (by intention-to-treat) will determine differences in antibiotic consumption for superiority and COPD health status for non-inferiority. Secondary outcomes include: COPD health status, CCQ domain scores, use of other COPD treatments (weeks 1, 2 and 4), EQ-5D utility scores (weeks 1, 2 and 4 and month 6), disease-specific, health-related quality of life (HRQoL) at 6 months, all-cause antibiotic consumption (antibiotic use for any condition) during first 4 weeks post randomisation, total antibiotic consumption (number of days during first 4 weeks of antibiotic consumed for AECOPD/any reason), antibiotic prescribing at the index consultation and during following 4 weeks, adverse effects over the first 4 weeks, incidence of pneumonia (weeks 4 and 6 months), health care resource use and cost comparison over the 6 months following randomisation. Prevalence and resistance profiles of bacteria will be assessed using throat and sputum samples collected at baseline and 4-week follow-up. A health economic evaluation and qualitative process evaluation will be carried out. DISCUSSION: If shown to be effective (i.e. leads to a reduction in antibiotic use with no worse COPD health status), the use of the CRP POCT could lead to better outcomes for patients with AECOPD and help reduce selective pressures driving the development of antimicrobial resistance. PACE will be one of the first studies to evaluate the cost-effectiveness of a POCT biomarker to guide clinical decision-making in primary care on patient-reported outcomes, antibiotic prescribing and antibiotic resistance for AECOPD. TRIAL REGISTRATION: ISRCTN registry, ID: ISRCTN24346473 . Registered on 20 August 2014.

The Diagnosis of Urinary Tract infection in Young children (DUTY): a diagnostic prospective observational study to derive and validate a clinical algorithm for the diagnosis of urinary tract infection in children presenting to primary care with an acute illness.

BACKGROUND: It is not clear which young children presenting acutely unwell to primary care should be investigated for urinary tract infection (UTI) and whether or not dipstick testing should be used to inform antibiotic treatment. OBJECTIVES: To develop algorithms to accurately identify pre-school children in whom urine should be obtained; assess whether or not dipstick urinalysis provides additional diagnostic information; and model algorithm cost-effectiveness. DESIGN: Multicentre, prospective diagnostic cohort study. SETTING AND PARTICIPANTS: Children < 5 years old presenting to primary care with an acute illness and/or new urinary symptoms. METHODS: One hundred and seven clinical characteristics (index tests) were recorded from the child's past medical history, symptoms, physical examination signs and urine dipstick test. Prior to dipstick results clinician opinion of UTI likelihood ('clinical diagnosis') and urine sampling and treatment intentions ('clinical judgement') were recorded. All index tests were measured blind to the reference standard, defined as a pure or predominant uropathogen cultured at ≥ 10(5) colony-forming units (CFU)/ml in a single research laboratory. Urine was collected by clean catch (preferred) or nappy pad. Index tests were sequentially evaluated in two groups, stratified by urine collection method: parent-reported symptoms with clinician-reported signs, and urine dipstick results. Diagnostic accuracy was quantified using area under receiver operating characteristic curve (AUROC) with 95% confidence interval (CI) and bootstrap-validated AUROC, and compared with the 'clinician diagnosis' AUROC. Decision-analytic models were used to identify optimal urine sampling strategy compared with 'clinical judgement'. RESULTS: A total of 7163 children were recruited, of whom 50% were female and 49% were < 2 years old. Culture results were available for 5017 (70%); 2740 children provided clean-catch samples, 94% of whom were ≥ 2 years old, with 2.2% meeting the UTI definition. Among these, 'clinical diagnosis' correctly identified 46.6% of positive cultures, with 94.7% specificity and an AUROC of 0.77 (95% CI 0.71 to 0.83). Four symptoms, three signs and three dipstick results were independently associated with UTI with an AUROC (95% CI; bootstrap-validated AUROC) of 0.89 (0.85 to 0.95; validated 0.88) for symptoms and signs, increasing to 0.93 (0.90 to 0.97; validated 0.90) with dipstick results. Nappy pad samples were provided from the other 2277 children, of whom 82% were < 2 years old and 1.3% met the UTI definition. 'Clinical diagnosis' correctly identified 13.3% positive cultures, with 98.5% specificity and an AUROC of 0.63 (95% CI 0.53 to 0.72). Four symptoms and two dipstick results were independently associated with UTI, with an AUROC of 0.81 (0.72 to 0.90; validated 0.78) for symptoms, increasing to 0.87 (0.80 to 0.94; validated 0.82) with the dipstick findings. A high specificity threshold for the clean-catch model was more accurate and less costly than, and as effective as, clinical judgement. The additional diagnostic utility of dipstick testing was offset by its costs. The cost-effectiveness of the nappy pad model was not clear-cut. CONCLUSIONS: Clinicians should prioritise the use of clean-catch sampling as symptoms and signs can cost-effectively improve the identification of UTI in young children where clean catch is possible. Dipstick testing can improve targeting of antibiotic treatment, but at a higher cost than waiting for a laboratory result. Future research is needed to distinguish pathogens from contaminants, assess the impact of the clean-catch algorithm on patient outcomes, and the cost-effectiveness of presumptive versus dipstick versus laboratory-guided antibiotic treatment. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

A randomised placebo-controlled trial of oral and topical antibiotics for children with clinically infected eczema in the community: the ChildRen with Eczema, Antibiotic Management (CREAM) study.

BACKGROUND: Secondary skin infection is common during eczema exacerbations and many children are treated with antibiotics when this is suspected, although there is little high-quality evidence to justify this practice. OBJECTIVE: To determine the clinical effectiveness of oral and topical antibiotics, in addition to standard treatment with emollients and topical corticosteroids, in children with clinically infected eczema. DESIGN: Multicentre randomised, double-blind, placebo-controlled trial. SETTING: General practices and dermatology clinics in England, Wales and Scotland. PARTICIPANTS: Children (aged 3 months to < 8 years) with a diagnosis of eczema (according to U.K. Working Party definition) and clinical suspicion of infection. INTERVENTIONS: (1) Oral flucloxacillin and topical placebo; (2) topical fusidic acid (Fucidin(®), Leo Laboratories Limited) and oral placebo; and (3) oral and topical placebos, all for 1 week. MAIN OUTCOME MEASURES: Patient-Orientated Eczema Measure (POEM) at 2 weeks (assessing subjective severity in the week following treatment). RESULTS: We randomised 113 children (36 to oral antibiotic, 37 to topical antibiotic and 40 to placebo), which was fewer than our revised target sample size of 282. A total of 103 (92.0%) children had one or more clinical features suggestive of infection and 78 (69.6%) children had Staphylococcus aureus cultured from a skin swab. Oral and topical antibiotics resulted in a 1.52 [95% confidence interval (CI) -1.35 to 4.40] and 1.49 (95% CI -1.55 to 4.53) increase (worse subjective severity) in POEM score at 2 weeks, relative to placebo and controlling for baseline POEM score. Eczema Area and Severity Index (objective severity) scores were also higher (worse) in the intervention groups, at 0.20 (95% CI -0.12 to 0.52) and 0.42 (95% CI 0.09 to 0.75) for oral and topical antibiotics, respectively, at 2 weeks. Analyses of impact on the family, quality of life, daily symptom scores, and longer-term outcomes were all consistent with the finding of no or limited difference and a trend towards worse outcomes in the intervention groups. Sensitivity analyses, including adjusting for compliance and imputation for missing data, were consistent with the main findings. CONCLUSIONS: Our data suggest that oral and topical antibiotics have no effect, or a harmful effect, on subjective eczema severity in children with clinically infected eczema in the community. The CIs around our estimates exclude a meaningful beneficial effect (published minimal clinically important difference for POEM is 3.4). Although most patients in this trial had features suggestive of infection and S. aureus on their skin, participants primarily had mild-moderate eczema and those with signs of more severe infection were often excluded. Clinicians should consider avoiding oral and topical antibiotic use in children with suspected infected eczema in the community who do not have signs of 'severe infection'. Further research should seek to understand how best to encourage the use of topical steroids and limit use of antibiotics in those with eczema flares without signs of severe infection, as well as developing tools to better phenotype eczema flares, in order to better define a population that may benefit from antibiotic treatment. TRIAL REGISTRATION: European Union Drug Regulating Authorities Clinical Trials (EudraCT) number 2011-003591-37 and Current Controlled Trials ISRCTN96705420. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

Point of care testing for urinary tract infection in primary care (POETIC): protocol for a randomised controlled trial of the clinical and cost effectiveness of FLEXICULT™ informed management of uncomplicated UTI in primary care.

BACKGROUND: Urinary tract infections (UTI) are the most frequent bacterial infection affecting women and account for about 15% of antibiotics prescribed in primary care. However, some women with a UTI are not prescribed antibiotics or are prescribed the wrong antibiotics, while many women who do not have a microbiologically confirmed UTI are prescribed antibiotics. Inappropriate antibiotic prescribing unnecessarily increases the risk of side effects and the development of antibiotic resistance, and wastes resources. METHODS/DESIGN: 614 adult female patients will be recruited from four primary care research networks (Wales, England, Spain, the Netherlands) and individually randomised to either POCT guided care or the guideline-informed 'standard care' arm. Urine and stool samples (where possible) will be obtained at presentation (day 1) and two weeks later for microbiological analysis. All participants will be followed up on the course of their illness and their quality of life, using a 2 week self-completed symptom diary. At 3 months, a primary care notes review will be conducted for evidence of further evidence of treatment failures, recurrence, complications, hospitalisations and health service costs. DISCUSSION: Although the Flexicult™ POCT is used in some countries in routine primary care, it's clinical and cost effectiveness has never been evaluated in a randomised clinical trial. If shown to be effective, the use of this POCT could benefit individual sufferers and provide evidence for health care authorities to develop evidence based policies to combat the spread and impact of the unprecedented rise of infections caused by antibiotic resistant bacteria in Europe. TRIAL REGISTRATION NUMBER: ISRCTN65200697 (Registered 10 September 2013).

Probiotics for Antibiotic-Associated Diarrhoea (PAAD): a prospective observational study of antibiotic-associated diarrhoea (including Clostridium difficile-associated diarrhoea) in care homes.

BACKGROUND: Antibiotic prescribing rates in care homes are higher than in the general population. Antibiotics disrupt the normal gut flora, sometimes causing antibiotic-associated diarrhoea (AAD). Clostridium difficile (Hall and O'Toole 1935) Prévot 1938 is the most commonly identified cause of AAD. Little is known either about the frequency or type of antibiotics prescribed in care homes or about the incidence and aetiology of AAD in this setting. OBJECTIVES: The Probiotics for Antibiotic-Associated Diarrhoea (PAAD) study was designed as a two-stage study. PAAD stage 1 aimed to (1) prospectively describe antibiotic prescribing in care homes; (2) determine the incidence of C. difficile carriage and AAD (including C. difficile-associated diarrhoea); and (3) to consider implementation challenges and establish the basis for a sample size estimation for a randomised controlled trial (RCT) of probiotic administration with antibiotics to prevent AAD in care homes. If justified by PAAD stage 1, the RCT would be implemented in PAAD stage 2. However, as a result of new evidence regarding the clinical effectiveness of probiotics on the incidence of AAD, a decision was taken not to proceed with PAAD stage 2. DESIGN: PAAD stage 1 was a prospective observational cohort study in care homes in South Wales with up to 12 months' follow-up for each resident. SETTING: Recruited care homes had management and owner's agreement to participate and three or more staff willing to take responsibility for implementing the study. PARTICIPANTS: Eleven care homes were recruited, but one withdrew before any residents were recruited. A total of 279 care home residents were recruited to the observational study and 19 withdrew, 16 (84%) because of moving to a non-participating care home. MAIN OUTCOME MEASURES: The primary outcomes were the rate of antibiotic prescribing, incidence of AAD, defined as three or more loose stools (type 5-7 on the Bristol Stool Chart) in a 24-hour period, and C. difficile carriage confirmed on stool culture. RESULTS: Stool samples were obtained at study entry from 81% of participating residents. Over half of the samples contained antibiotic-resistant isolates, with Enterobacteriaceae resistant to ciprofloxacin in 47%. Residents were prescribed an average of 2.16 antibiotic prescriptions per year [95% confidence interval (CI) 1.90 to 2.46]. Antibiotics were less likely to be prescribed to residents from dual-registered homes. The incidence of AAD was 0.57 (95% CI 0.41 to 0.81) episodes per year among those residents who were prescribed antibiotics. AAD was more likely in residents who were prescribed co-amoxiclav than other antibiotics and in those residents who routinely used incontinence pads. AAD was less common in residents from residential homes. CONCLUSIONS: Care home residents, particularly in nursing homes, are frequently prescribed antibiotics and often experience AAD. Antibiotic resistance, including ciprofloxacin resistance, is common in Enterobacteriaceae isolated from the stool of care home residents. Co-amoxiclav is associated with greater risk of AAD than other commonly prescribed antibiotics. TRIAL REGISTRATION: Current Controlled Trials ISRCTN 7954844. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 18, No. 63. See the NIHR Journals Library website for further project information.

The diagnosis of urinary tract infections in young children (DUTY): protocol for a diagnostic and prospective observational study to derive and validate a clinical algorithm for the diagnosis of UTI in children presenting to primary care with an acute illness.

BACKGROUND: Urinary tract infection (UTI) is common in children, and may cause serious illness and recurrent symptoms. However, obtaining a urine sample from young children in primary care is challenging and not feasible for large numbers. Evidence regarding the predictive value of symptoms, signs and urinalysis for UTI in young children is urgently needed to help primary care clinicians better identify children who should be investigated for UTI. This paper describes the protocol for the Diagnosis of Urinary Tract infection in Young children (DUTY) study. The overall study aim is to derive and validate a cost-effective clinical algorithm for the diagnosis of UTI in children presenting to primary care acutely unwell. METHODS/DESIGN: DUTY is a multicentre, diagnostic and prospective observational study aiming to recruit at least 7,000 children aged before their fifth birthday, being assessed in primary care for any acute, non-traumatic, illness of ≤ 28 days duration. Urine samples will be obtained from eligible consented children, and data collected on medical history and presenting symptoms and signs. Urine samples will be dipstick tested in general practice and sent for microbiological analysis. All children with culture positive urines and a random sample of children with urine culture results in other, non-positive categories will be followed up to record symptom duration and healthcare resource use. A diagnostic algorithm will be constructed and validated and an economic evaluation conducted.The primary outcome will be a validated diagnostic algorithm using a reference standard of a pure/predominant growth of at least >103, but usually >105 CFU/mL of one, but no more than two uropathogens.We will use logistic regression to identify the clinical predictors (i.e. demographic, medical history, presenting signs and symptoms and urine dipstick analysis results) most strongly associated with a positive urine culture result. We will then use economic evaluation to compare the cost effectiveness of the candidate prediction rules. DISCUSSION: This study will provide novel, clinically important information on the diagnostic features of childhood UTI and the cost effectiveness of a validated prediction rule, to help primary care clinicians improve the efficiency of their diagnostic strategy for UTI in young children.

In vitro assessment of colistin's antipseudomonal antimicrobial interactions with other antibiotics.

OBJECTIVE: To study the interactions of colistin (MIC 2 mg/L) at concentrations of 0.5 and 5 mg/L with ceftazidime (1 and 75 mg/L, MIC 0.5 mg/L), aztreonam (1 and 30 mg/L, MIC 0.12 mg/L), meropenem (1 and 25 mg/L, MIC 0.03 mg/L), gentamicin (1 and 10 mg/L, MIC 2 mg/L), piperacillin (5 and 100 mg/L, MIC 4 mg/L) and ciprofloxacin (0.25 and 4 mg/L, MIC 1 mg/L) using a representative strain of Pseudomonas aeruginosa isolated from a cystic fibrosis patient. METHODS: The method used was a bacterial time kill curve with single agents and combinations. Using inocula of 106 CFU/mL, multiple sampling was performed over 6 h and in triplicate. The AUBKC of the time versus viable count curve, with single agents and combinations of agents, was taken as the endpoint for comparison. RESULTS: For colistin plus ceftazidime, colistin plus aztreonam, colistin plus meropenem and colistin plus ciprofloxacin, the pattern was for all the combinations (high or low concentrations) to produce smaller AUBKCs than single agents. In experiments using a bacteriostatic agent such as ceftazidime, the AUBKCs (log CFU/µL per h) for colistin 0.5 mg/L or 5 mg/L alone were 32.3±0.8 or 12.7±0.5, and for ceftazidime 1 mg/L or 75 mg/L alone they were 24.3±1.5 or 20.9±2.7. Combinations of colistin 0.5 mg/L plus either ceftazidime 1 mg/L or 75 mg/L produced AUBKCs of 23.8±1.8 or 16.1 mg/L. Combinations of colistin 5 mg/L plus ceftazidime 1 mg/L or 75 mg/L produced AUBKCs of 12.2±0.8 or 8.7±1.0. The AUBKCs for colistin 5 mg/L plus 75 mg/L are significantly smaller than those for the single agents, indicating synergy. In experiments using the bactericidal agent ciprofloxacin, the AUBKCs (log CFU/mL per h) for colistin 0.5 mg/L or 5 mg/L alone were 33.6±1.9 or 11.2±2.4, and for ciprofloxacin 0.25 mg/L or 4 mg/L alone they were 32.8±1.3 or 5.0±0.7. Combinations of colistin 0.5 mg/L plus either ciprofloxacin 0.25 mg/L or 4 mg/L produced AUBKCs of 32.2±0.9 or 4.3±1.4. Combinations of colistin 5 mg/L plus ciprofloxacin 0.25 mg/L or 4 mg/L produced AUBKCs of 10.7±1.5 or 4.2±0.6. Although combination AUBKCs were smaller than those for single agents, in no case did this reach statistical significance (p<0.05). CONCLUSIONS: These studies indicate that addition of colistin to other antipseudomonal drugs tends to produce smaller AUBKCs and hence greater killing of Pseudomonas aeruginosa than monotherapy.