Cost-effectiveness of urinary dipsticks to screen asymptomatic catheter-associated urinary infections in an intensive care unit Tissot E, Woronoff-Lemsi M C, Cornette C, Plesiat P, Jacquet M, Capellier G Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The study examined the use of urinary dipsticks (UDs; Multistix 8-SG) to screen asymptomatic catheterised patients for catheter-associated urinary tract infections (UTIs). Four combinations of the leukocyte (L) test pad and the nitrite (N) test pad were calculated. These were L and N, L or N, L alone and N alone. The UDs were analysed by reflectance spectrophotometry (Clinitek 50) The comparator was quantitative urine culture (QUC). Type of intervention Screening. Economic study type Cost-effectiveness analysis. Study population The study population consisted of all consecutive asymptomatic hospitalised patients in a 15-bed medical intensive care unit. This was in addition to catheterised patients without symptoms of UTI (fever of greater than 38 degrees C, dysuria or suprapubic tenderness). The physicians decided on the lack of symptoms. Patients without urinary catheterisation, or with symptoms of catheter-associated UTI at the time of sampling, were excluded. Setting The setting was a hospital. The economic study was carried out in Besancon University hospital, France. Dates to which data relate The effectiveness and cost data were collected between 1 March and 31 August 1998. The price year was 1998. Source of effectiveness data The effectiveness data were derived from a single study. Link between effectiveness and cost data The resource data were taken from the same patient sample as the effectiveness data. The data were collected prospectively. Study sample The sample comprised all consecutive, asymptomatic catheterised patients at the hospital. The ratio of males to females was 1.9 and the average age of the sample was 56 years. No power calculations to determine the sample size were reported. The study sample was appropriate for the clinical study question, as the patients were catheterised and the Page: 1 / 5
most frequently isolated uropathogens have no nitrate reductase activity. A total of 339 urine samples from 144 patients were analysed. Subsequently, 22 patients were excluded from the study because they were not catheterised (17) or had symptoms of catheter-associated UTI (5). The mean number of samples taken per patient was 2.6. Study design This was a prospective cohort study carried out in a single centre. On patient admission, and thereafter once a week, a QUC and a UD were performed on the same urine sample. The length of follow-up was 6 months. Analysis of effectiveness The clinical study was analysed on an intention to treat basis. The health outcome used in the analysis was the number of asymptomatic catheter-associated UTIs. The performance of the different screening methods was assessed using the specificity, sensitivity, positive predictive value and negative predictive value. Since the strategies were performed on the same sample, issues concerning comparability, confounding and selection bias were minimised. The paper provided baseline characteristics of the patients. Effectiveness results The performance decreased with the positive level of QUC for all combinations. The incidence of asymptomatic catheter-associated UTIs was 31.1% (at least 10^5 organisms/ml). The effectiveness (sensitivity) was 1 for QUC and 0.872 for UDs (L or N combination). In the UD strategy, the L or N combination was the better combination with which to screen catheterised patients for catheter-associated UTIs. The sensitivity was 87.2% (95% confidence interval, CI: 78.4-96.0), the specificity was 61.6%, the positive predictive value was 30.6%, and the negative predictive value was 96.1% (95% CI: 93.3-98.9). A total of 157 (46.3%) UDs were positive for L or N combination. Only 7 false-negative results were observed with this combination. All false-negative results were observed with patients with haematuria and 86% (6 out of 7) of the patients with proteinuria. The performance of the leukocyte test pad alone was nearly equal to the performance of the L or N combination. Clinical conclusions The authors concluded that UDs are an effective rapid test for screening for asymptomatic, catheter-associated UTIs in intensive care unit patients. Measure of benefits used in the economic analysis The outcome measure used for the economic analysis was the performance of the screening tests in terms of the number of catheter-associated UTIs detected by each strategy. Direct costs Discounting was not carried out, which was appropriate since the costs were incurred in less than 2 years. The quantities and the costs were analysed separately. The human resource costs (nurses) were calculated for both screening methods. The QUC costs were derived from the costs of microscopic examination and culture, with or without antibiotic sensitivity. The cost data were obtained from the hospital's 1998 accountancy records. The costs of the UD strategy were for the dipsticks (Multi 8 SG) and the automated Clinitek 50. The unit cost of using automation was calculated, allowing for 5-years' depreciation. The quantities and costs were estimated using actual data. The quantities were measured in 1998 and the price year was also 1998. Statistical analysis of costs Page: 2 / 5
All continuous variables were presented as the mean values, along with the 95% CIs. Indirect Costs No indirect costs were measured, as the study was based on a provider perspective. Currency The currency was French francs (Ffr). These were converted into Euros (EUR) using a conversion rate of 1 EUR = Ffr 6.56. Sensitivity analysis One-way sensitivity analyses were carried out to determine the degree to which the uncertainty of different parameters could influence the cost-effectiveness results. A univariate sensitivity analysis was used to analyse parameters such as the unit costs of QUC (varied by +/- 50%; EUR 10.7-32.2), the percentage of positive dipsticks (0.3-0.7), and the sensitivity of L or N combinations (0.6-0.95). A multivariate analysis was also carried out on the incremental costeffectiveness ratio (ICER) under preservative conditions. These were a unit cost of EUR 10.7 for QUC, 0.7% positive dipsticks, and a sensitivity of 0.6 for the L or N combination. Estimated benefits used in the economic analysis The number of cases detected by each strategy was not explicitly reported (see the 'Synthesis of Costs and Benefits' section). Cost results The total cost of the QUC was EUR 21.5 per test. The total cost of the UD was EUR 12.6. Synthesis of costs and benefits The ICER of QUC was EUR 69.5 per case of detected asymptomatic, catheter-associated UTI. The results of the oneway sensitivity analysis were sensitive to the three parameters under study. When the sensitivity of the L or N combination was 0.789, as observed with a positive level of QUC of at least 10^4 organisms/ml, the ICER of QUC was EUR 39.8 per case of detected asymptomatic, catheter-associated UTI. Under preservative conditions QUC was dominant, being more efficacious and cost-saving than UDs. The ICER was EUR -0.5 per case of detected asymptomatic, catheter-associated UTI. Authors' conclusions Although the quantitative urine culture (QUC) strategy was more effective and more costly, the authors concluded that the urinary dipstick (UD) was a rapid and cost-effective test with which to screen asymptomatic catheterised patients for QUC in a medical intensive care unit. The UD strategy decreased the cost of nosocomial infection diagnosis and the daily workload in the microbiology laboratory. CRD COMMENTARY - Selection of comparators The comparator was explicitly stated and justified (in effect the 'gold' standard test). You should decide whether this is a widely used test in your own setting. Validity of estimate of measure of effectiveness The study design appears to have been appropriate for the study question. Since both testing methods were performed Page: 3 / 5
on the same group of patients, there was no need to randomise and no possibility of bias due to confounding. The study population appears to have been representative of those who would need catheterisation. The authors made an assumption that the sensitivity of QUC was 100%, as it was their reference strategy. However, there is no reason to doubt this assumption. The effectiveness results should have high validity. Validity of estimate of measure of benefit The benefit measure was derived from the effectiveness results, although the number of catheter-associated UTIs detected by each strategy was not explicitly stated. Validity of estimate of costs The perspective from which the study was conducted was stated, and all the relevant costs appear to have been included. The price year was reported, and the resource quantities and the unit costs were reported separately. The unit costs and prices were generalisable to other settings, especially in Europe, as the costs were converted to a unit of currency used in these countries. Other issues The authors highlighted a limitation of their study in that the results observed did not apply to symptomatic, catheterassociated UTI. The analysis included catheterised patients without symptoms of UTI. The authors compared their findings with those of other studies. Implications of the study The authors recommend that UDs can be used at the bedside with reflectance spectrophotometric analysis. Decisionmakers should be aware that the intervention of interest was less effective than the reference strategy (QUC). The costs and outcomes of false positive and negative results associated with UDs would need to be considered if a more inclusive cost-effectiveness analysis is to be provided. Source of funding None stated. Bibliographic details Tissot E, Woronoff-Lemsi M C, Cornette C, Plesiat P, Jacquet M, Capellier G. Cost-effectiveness of urinary dipsticks to screen asymptomatic catheter-associated urinary infections in an intensive care unit. Intensive Care Medicine 2001; 27(12): 1842-1847 PubMedID 11797017 DOI 10.1007/s00134-001-1134-0 Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Cross Infection /etiology /prevention & control /urine; Female; France; Humans; Intensive Care Units /economics; Male; Mass Screening /economics; Middle Aged; Prospective Studies; Reagent Strips /economics; Sensitivity and Specificity; Urinary Catheterization /adverse effects; Urinary Tract Infections /etiology /prevention & control /urine Page: 4 / 5
Powered by TCPDF (www.tcpdf.org) AccessionNumber 22002000192 Date bibliographic record published 30/06/2003 Date abstract record published 30/06/2003 Page: 5 / 5