Yield and cost of individual common diagnostic tests in new primary care outpatients in Japan

BACKGROUND

Appropriate diagnostic testing involves considerations of cost-effectiveness. We examined the cost-effectiveness of individual tests in a panel of tests defined by the Japan Society of Clinical Pathology.

METHODS

We studied 540 new, symptomatic primary care outpatients with a set of 30 common diagnostic tests [the Essential Laboratory Tests (2); ELT(2) panel] for clinical evaluation and identification of occult disease. A useful result (UR) of testing was defined as a finding that contributed to a change in a physician's diagnosis or decision-making relating to a "tentative initial diagnosis" obtained from history and physical examination alone.

RESULTS

The ELT(2) panel testing yielded 398 URs and uncovered 261 occult diseases among 540 patients. In total, 1592 tests contributed to either UR-generation or discovery of occult disease. The cost per effective test (cost required per test that contributed to either definition of effectiveness) ranged from 108 yen (approximately 0.92 US dollars) for total cholesterol to 6200 yen (approximately 52.50 dollars) for chest x-ray. Contribution rates and the cost per effective test varied among disease categories. We restructured panel components considering the effectiveness of each test. Subsets of the ELT(2) would have improved cost-effectiveness and achieved cost savings in five of eight disease categories.

CONCLUSIONS

Assembly of tests based on cost-effectiveness can improve clinical efficiency and decrease total cost of panel testing for selected patient groups.

Cost-effectiveness of screening swab or urine specimens for Chlamydia trachomatis from young Canadian women in Ontario

BACKGROUND

Undetected and untreated Chlamydia trachomatis infections can result in a significant health burden. Diagnostic testing refers to tests performed on patients with symptoms, whereas screening refers to testing specimens in asymptomatic patients. The goal of diagnostic testing and screening programs are early identification of infections to prevent upper tract infection and transmission to other partners.

GOAL

To compare the costs and outcomes of alternative diagnostic testing and screening programs for women ages 15 to 24 years in the province of Ontario, Canada.

STUDY DESIGN

Using outcome probabilities from the literature and a consensus group, together with the costs from insurance billing, a decision analytic model was constructed to determine the baseline risk of C trachomatis and related sequelae. Seven diagnostic testing and screening programs were compared over a 10-year period. The programs compared included the use of nucleic acid amplification assays collected from urine or endocervical swab specimens.

RESULTS

Largely because of lower sensitivity the urine-based testing or screening programs were dominated by the swab-based programs. The move from swab-based testing to a swab-based screening program for high-risk women costs $1873 per case of C trachomatis averted. Expanding the program further to include all women in Ontario between 15 and 24 years of age is considerably more costly at $5990 per case averted.

CONCLUSIONS

It is more costly and more effective to screen and treat high-risk women ages 15 to 24 years for C trachomatis than to perform only swab-based diagnostic testing on symptomatic women. Expanding the screening program to include all women ages 15 to 24 years is considerably more expensive and only moderately more effective than screening only high-risk women.

The cost of on-site versus off-site workplace urinalysis testing for illicit drug use

Workplace drug testing has become standard business practice in America. With increasing costs, however, many corporations look for more cost-effective testing alternatives. The study compared the cost of two testing strategies: urinalysis at the work site versus testing that occurs elsewhere. Employees from seven company locations were tested for illicit drugs. Four sites conducted the initial screening test at the workplace and three sites performed testing off site. On-site testing was found to have significantly lower variable costs, and total costs were lower once a threshold of 27 employees tested was attained. On-site testing also provided immediate access to negative test results, thereby facilitating personnel decisions.

Imagecytometry: a new tool for diagnosis of glomerular haematuria

Differentiation between glomerular and nonglomerular haematuria is a major challenge in clinical medicine, which is very important for a definitive diagnosis and management in individual cases. Phase contrast microscopy of red cells in urine is the standard practice for diagnosis of glomerular haematuria. Urine cell flowcytometry is recently being used for such diagnosis. In this context, the role of determination of haemoglobin content of urine red cells is not know. Application of image analysis to study the red cells in urine may be more objective and accurate for the diagnosis. The present study has been undertaken to evaluate the urine red cells with the help of an automated computerized image analysis system for determination of hemoglobin content by integrated optical density (IOD). The morphometric parameters were also analyzed. The glomerular RBCs were significantly smaller in diameter, area and perimeter than nonglomerular RBCs with a greater variation in shape and lower [OD (p<0.0001 to <0.00002). With the help of morphometric parameters the percentage of cases diagnosed correctly varied from 90 to 95. The IOD helped to diagnose 100% cases. Thus application of this new technique may be very useful diagnostic tool in the investigation of haematuria.

How effective are screening tests for microalbuminuria in random urine specimens?

The effectiveness of four urine screening tests-microalbumin (MAlb), total protein (TProt), total protein/creatinine ratio (TProt/Cr R), and dipstick (DPalb) test for albumin-were evaluated for the detection of MAlb in random urine specimens. The following criteria were used to assess the effectiveness of each urine screening test: 100% specificity (no false positive results); cost effectiveness; rapidity and ease of performing the screening test; and increased laboratory efficiency. A "gold standard" for presence of MAlb in random urine samples was defined as a microalbumin/creatinine ratio (MAlb/Cr R) of > or = 30 mg/g. The least costly urine screening test was the DPalb, which, if assigned a value of 1.0, allowed a cost ranking order for the screening tests-DPalb (1.0) < urine TProt (1.03) < urine TProt/Cr R (2.1) < urine MAlb (7.0). Two hundred urine samples from diabetic inpatients and outpatients were tested. Only two screening tests--MAlb and DPalb--achieved 100% specificity without increasing laboratory costs (small net savings), whereas the other two screening tests--TProt and TProt/Cr R-only achieved 100% specificity with increased laboratory costs. Theoretical prevalence rate analysis showed that urine MAlb screening would be effective at all prevalence rates for overt nephropathy. TProt and DPalb urine screening testing would be most effective in populations with prevalence rates of > or = 15% for overt nephropathy. The TProt/Cr R ratio would only be effective in populations with prevalence rates of > or = 30%. Of the four urine screening tests, only DPalb would significantly streamline the process of measuring urine MAlb. The dipstick test is inexpensive, easy and rapid to perform, does not delay measuring the ratio, since there is no wait for the screening test result, and can be used by referring laboratories to screen urine specimens before they are submitted to a central laboratory, thereby reducing laboratory workload.

Opportunistic discovery of occult disease by use of test panels in new, symptomatic primary care outpatients: yield and cost of case finding

BACKGROUND

Diagnostic test panels have been advocated by the Japan Society of Clinical Pathology for evaluation of presenting complaints of new outpatients in primary care medicine. The tests have additional potential utility for opportunistic finding of asymptomatic diseases, but data are lacking on the number of new conditions identified by the test panels and on the cost per identified case.

METHODS

We studied 540 new, symptomatic patients at the Comprehensive Medicine Clinics of National Defense Medical College during 1991-1997. All underwent testing with the "Essential Laboratory Tests" panel (2) [ELT(2) panel]. This panel includes hematologic tests, urinalysis, total protein, C-reactive protein, albumin, cholesterol, triglycerides, glucose, urea nitrogen, creatinine, uric acid, serum protein fractionation, six enzymes, and optional tests, including x-rays, electrocardiogram, and fecal occult blood.

RESULTS

The ELT(2) panel uncovered 276 additional diagnoses of asymptomatic disease or abnormal health status. The most frequent occult condition was hyperlipidemia (100 cases) followed by liver dysfunction (53 cases). Clinical efficiency of the panel (occult diseases/patient) varied depending on the category of tentative initial diagnosis, with the highest efficiency in patients with cardiovascular disease. We created smaller panels by combining 11 basic tests [called the ELT(1) baseline panel] with one or more additional tests from the ELT(2) and analyzed their cost-effectiveness. Addition of four tests (total cholesterol, alanine aminotransferase, glucose, and uric acid) improved both clinical efficiency (0.41 occult disease/patient) and economic efficiency [ 2372 yen (approximately $22.50 US)/occult disease] at a cost-effectiveness of 177 yen per incremental case of occult disease. Addition of further tests decreased cost-effectiveness.

CONCLUSIONS

Although the ELT(2) panel has supplemental utility for opportunistic screening of some significant, occult diseases and conditions, universal utilization of the full panel is not supported by the cost-effectiveness found in this study.

A new automated system for urine analysis: a simple, cost-effective and reliable method for distinguishing between glomerular and nonglomerular sources of haematuria

OBJECTIVE

To determine the ability, reliability and accuracy of a new automated system of urine analysis in differentiating glomerular from nonglomerular bleeding in the initial investigation of haematuria, and compare its efficacy with conventional phase-contrast microscopy (PCM).

PATIENTS AND METHODS

One hundred and six urine samples from patients in whom the final diagnosis was available were analysed using electrical flow impedance to detect, enumerate and size red blood cells in a conductive fluid (the cellfacts analyser, Microbial Systems Ltd, Coventry, UK). All the samples were also tested using a dipstick method and PCM was carried out for comparison on 45 of the 106 urine specimens. The results of cellfacts analysis were correlated with the final diagnoses to assess sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of this method; the costs were also analysed.

RESULTS

Sixty-nine urine samples tested positive for blood on dipstick urine analysis and all these were confirmed to have red blood cells on cellfacts analysis. The remaining 37 samples were negative for blood on dipstick testing and cellfacts analysis, although seven patients had been referred with previously detected microscopic haematuria, none of whom were found to have any detectable pathology in the urinary tract on clinical examination and investigations. The remaining 30 patients were diagnosed to have urological or nephrological conditions with no haematuria. In the positive group, 20 (29%) patients were from the glomerular group, with a mean (range) red blood cell size of 4.25 (4-5.1) micrometer, and 49 (71%) from the nonglomerular group, with red blood cells of 5.47 (4.67-5.70) micrometer. These ranges overlapped at 4.67-5.1 micrometer at the decision threshold of 4.75 micrometer, the distribution of dysmorphic and eumorphic red blood cells for the glomerular group was 18 (90%) and two (10%), respectively, and for the nonglomerular group was 2 (4%) and 47 (96%), respectively. The sensitivity, specificity, PPV and NPV were 90%, 96%, 90% and 96%, respectively. Consumable and labour costs were very low.

CONCLUSIONS

Cellfacts analysis is a simple, rapid, objective and cost-effective method for differentiating glomerular from nonglomerular urinary red blood cells, especially when few such cells are present.

Evaluation of Sysmex UF-100 urine flow cytometer vs chamber counting of supravitally stained specimens and conventional bacterial cultures

We evaluated the Sysmex UF-100 urine flow cytometer (TOA Medical Electronics, Kobe, Japan) with 269 uncentrifuged urine specimens by comparing it with Sternheimer staining and particle counting in 1-microL disposable chambers with both brightfield and phase-contrast microscopy (the reference method). Results of routine test strip analysis, sediment microscopy (182 specimens), and bacterial culture (204 specimens) were also available. Detection of urinary WBCs and RBCs was highly reliable with the UF-100 compared with manual chamber counting (r = .98 and .88, respectively). Identification of bacteria was equal to that with visual microscopy of uncentrifuged specimens; sensitivity was 55%, and specificity 90%, compared with bacterial cultures at a cutoff of > 10(3) colony-forming units per milliliter. Renal damage was difficult to evaluate even with manual methods because of the low counts of renal tubular cells and casts; with standard manual Sternheimer-stained sediment analysis, sensitivity was 65% to 69% and specificity 66% to 91%, compared with the uncentrifuged chamber method at a cutoff of 3 and 10 particles per microliter, respectively. Renal damage was demonstrated with the UF-100 with a sensitivity of 26% to 69% and specificity 92% to 94%, compared with chamber counts. Automated urinalysis with the UF-100 urine flow cytometer offers considerable savings in time and labor. When high sensitivity is needed, visual microscopic review should be performed to detect renal disease.

Screening for urinary tract infection in infants in the emergency department: which test is best?

OBJECTIVE

Comparison of rapid tests and screening strategies for detecting urinary tract infection (UTI) in infants.

METHODS

Cross-sectional study conducted in an urban tertiary care children's hospital emergency department and clinical laboratories of 3873 infants <2 years of age who had a urine culture obtained in the emergency department by urethral catheterization; results of urine dipstick tests for leukocyte esterase or nitrites, enhanced urinalysis (UA) (urine white blood cell count/mm3 plus Gram stain), Gram stain alone, and dipstick plus microscopic UA (white blood cells and bacteria per high-powered field) compared with urine culture results (positive urine results defined as >/=10 colony-forming units per milliliter of urinary tract pathogen) for each sample. Cost comparison of 1) dipstick plus culture of all urine specimens versus 2) cell count +/- Gram stain of urine, culture only those with positive results.

RESULTS

The enhanced UA was most sensitive at detecting UTI (94%; 95% confidence interval: 83,99), but had more false-positive results (16%) than the urine dipstick or Gram stain (3%). The most cost-effective strategy was to perform cultures on all infants and begin presumptive treatment on those whose dipstick had at least moderate (+2) leukocyte esterase or positive nitrite at a cost of $3.70 per child. With this strategy, all infants with UTI were detected. If the enhanced UA was used to screen for when to send the urine for culture, 82% of cultures would be eliminated, but 4% to 6% of infants with UTI would be missed and the cost would be higher ($6.66 per child).

CONCLUSION

No rapid test can detect all infants with UTI. Physicians should send urine for culture from all infants and begin presumptive treatment only on those with a significantly positive dipstick result. The enhanced UA is most sensitive for detecting UTI, but is less specific and more costly, and should be reserved for the neonate for whom a UTI should not be missed at first visit.

Screening dipstick urinalysis: a time to change

OBJECTIVE

This study attempted to determine the minimal cost of screening dipstick urinalyses in a hypothetical cohort of 2000 asymptomatic pediatric patients in a primary care setting.

METHODOLOGY

The minimal cost utilizing a private practitioner in an urban or suburban group pediatric setting was calculated. Costs were determined by using current charges for supplies ordered to perform tests in the office, charges for tests performed by a commercial laboratory, and the cost of an initial evaluation by a pediatric nephrologist. Data from published studies were also utilized.

RESULTS

Nine percent (179/2000) of patients were calculated to have an initial abnormal urinalysis. Upon retesting only 1.5% (29/2000) of patients were calculated to have a persistent abnormality. The calculated rate of a false positive/transient abnormality for all patients in the hypothetical cohort of 2000 asymptomatic pediatric patients was 84% (150/179). The calculated minimal cost for the outpatient evaluation of 2000 asymptomatic pediatric patients by dipstick urinalyses ranged between $5022 to $6475. The range depends on whether 50% versus 100% of patients with a repeat abnormal dipstick urinalysis were referred to a pediatric nephrologist for further evaluation. The calculated cost was $1290 to initially screen all 2000 patients with a dipstick urinalysis or 65 cents per patient. The calculated cost to evaluate the 29 patients with any persistent abnormality on repeat dipstick urinalysis was $3732 to $5185 or $129 to $179 per patient. This is the calculated cost for a single screening of 2000 asymptomatic pediatric patients. The calculated cost for four multiple screening urinalyses as currently recommended is $20 088 to $25 900. Additionally, these are only minimal initial calculated costs. Costs of any renal imagining or function studies ordered by the pediatric nephrologist or the pediatrician pursuing a further evaluation on his/her own were not included.

CONCLUSION

Multiple screening dipstick urinalyses in asymptomatic pediatric patients are costly and should be discontinued. In their place, we propose that a single screening dipstick urinalysis be obtained at school entry age, between 5 and 6 years old, in all asymptomatic children. The sample should be a first morning void.

[Megaloblastic anemia: rapid and economical study]

The diagnosis of megaloblastic anaemias caused by cobalamine or folate deficiency are still difficult. The dosage of these two substances help to differenciate between both carencies, but it is not determinant of any of them and is an expensive method. Homocisteinuria (HC), methylmalonuria (MMA) and formiminoglutamic acid (FIGLU) are cheap tests which could help in the differential diagnosis, if they are used properly. We report 62 patients to whom we made these test simultaneously. All of the patients received 10 micrograms of vit B12 and after 72 hours, 1 mg/day of folic acid (for 3 days). In both cases waiting for the increase of reticulocytyes up to 150 x 10(9)/L as a form of therapeutic test of diagnosis. By this simple way we have detected 97.9% of specificity for cobalamin deficiency of the MMA test, and only 4.2% for HC. This last test had increased its specificity up to 91.6% in association with the negative FIGLU test. We have also found a high specificity (92.3%) for FIGLU due to the detection of folate deficiency, in opposition with other authors who had described it as low as 50%. We have also compared the costs of the 3 tests with the dosage of cobalamine and folate, and we have found that the formers are 11 times less expensive than the last ones.

Dipstick only urinalysis screen for the pediatric emergency room

To determine if microscopic urinalysis is needed in all pediatric emergency room patients screened for urinary tract infections (UTI), we compared the dipstick urinalysis and complete urinalysis (dipstick and microscopy) with urine cultures in 236 children, aged 3 weeks to 21 years. The ability to detect UTI by dipstick only and by complete urinalysis was the same, however microscopic evaluation added many false-positive results without detecting additional UTIs. Because the ability to detect UTI (sensitivity) is maintained, we now offer a dipstick only urinalysis to our emergency room for children 2 years of age or older, with a microscopic analysis performed automatically if dipstick results are positive. If no microscopic urinalysis is required, testing turn-around time is reduced by 12.3 min/test and the hospital charge is reduced from U.S. $32 to U.S. $12.

Evaluation of a rapid screening filter test for urinary tract infection in children

OBJECTIVE

Clinical evaluation of a rapid screening filter test for urinary tract infection (UTI), FiltraCheck-UTI, comparison to the urine dipstick and conventional urinalysis for test performance and cost effectiveness in children.

SETTING

Pediatric emergency department at an urban children's hospital.

METHODS

Cross-sectional concordance study of 1298 children age 2 days to 19 years (50% < or = 2 years) for whom a urine culture was ordered; screening tests run by trained laboratory personnel; cost per case detected calculated; retrospective chart review for clinical information.

RESULTS

Prevalence of UTI was 7.1%. Urine obtained from children < or = 2 years by catheter (97%) as part of an evaluation of fever or sepsis (82%). FiltraCheck-UTI was comparable with microscopy for bacteriuria (P = 0.11), sensitivity of 85% (95% confidence interval, 76 to 91) and specificity of 72% (95% confidence interval, 70 to 75%) but it was difficult detect Gram-positive organisms by this method (P < 0.001). Its performance varied by definition of UTI. The urine dipstick had the best specificity and was the most cost-effective rapid test.

CONCLUSIONS

FiltraCheck-UTI is more expensive and has more false positives than the urine dipstick in detecting UTI in children. The dipstick continues to be the best inexpensive alternative to microscopy, but it is probably not an adequate screen for when to send a urine culture in young children.

Usefulness of blood cultures in pyelonephritis

To evaluate the usefulness of blood cultures in patients admitted with pyelonephritis, a retrospective chart review was-conducted of inpatients at a 594-bed urban, academic medical center from 1990 through 1992 with a primary discharge diagnosis of pyelonephritis. A total of 338 patients had this primary discharge diagnosis. One or more sets of blood cultures were obtained in 307 patients (91%). Fifty-six (18%) patients had a positive blood culture; 24 (32%) positive blood cultures grew coagulase-negative Staphylococcus species, in all but two instances considered a skin contaminant. Of the blood cultures drawn, only 1 (0.2%) grew a pathogenic organism not found in the urine culture, with no impact on clinical management. These results support the conclusion that blood cultures are rarely clinically useful and seldom vary from urine culture results. Potential annual cost savings of between $10 million and $20 million in the United States could result from eliminating routine blood cultures in the setting of uncomplicated acute pyelonephritis.

Patterns of care received by Medicaid recipients with urinary tract infections

BACKGROUND

Urinary tract infections (UTIs) occur commonly in children and may lead to substantial morbidity. Most experts recommend urine cultures for diagnosing UTIs in children. In addition, most experts recommend imaging studies in a portion of children diagnosed with UTIs.

PURPOSE

The purpose of this study was to assess how rates of performance of urine cultures and imaging studies for children in the Alabama Medicaid program diagnosed with a UTI vary by patient demographics, provider characteristics, and service locations.

METHODS

The study design was a retrospective review of Alabama Medicaid claims data. Children were included as UTI cases if they had a Medicaid claim for urinary tract infections during 1991, were continuously enrolled in Medicaid for that year, and were younger than 8 years of age. Claims were grouped into episodes of care, and episodes were assigned to a diagnosing physician. Physician locations were classified as rural, suburban, or urban using demographic data. Specific laboratory and imaging procedures were identified using CPT codes (Physician's Current Procedural Technology Codes, 4th Edition).

RESULTS

We identified 404 episodes of UTI occurring in 380 children. Only 47% of episodes were associated with claims for urine cultures. Claims for urine cultures were more frequently filed by pediatricians in urban locations. In the subset of 114 patients with multiple UTI episodes, only 68% had imaging studies specific for the urinary tract. Only 44% received both a voiding cystourethrogram and renal ultrasound.

CONCLUSIONS

Claims data suggest that physicians underuse urine cultures in diagnosing UTIs in Alabama pediatric Medicaid recipients. Urban-based pediatricians perform better than other types of physicians. Imaging studies are also used less frequently than is commonly recommended.

Diagnostic regimes for urinary tract infection--are research results applied to practice?

A clinical audit of ward practice for diagnosing and treating urinary tract infection was carried out to assess the impact on clinical practice four years after publication of a working protocol. Data were collected from all medical, surgical, gynaecology and geriatric wards in 25 hospitals in Northern Ireland. All wards made use of urinary dipsticks for ward testing, as recommended by the protocol. However many negative samples were still forwarded for laboratory analysis. The potential financial savings which would result from effective ward screening were not being realised and the publication appeared to have minimal impact on clinical practice. Advice on an improved diagnostic protocol for urinary tract infection may not have been disseminated to the nursing staff whose role was pivotal in the screening process.

Urine microscopy on a counting chamber for diagnosis of urinary infection

Several quantitative methods of urine microscopic examination for bacteriuria and pyuria on a blood cell counting-chamber have been found reliable for the diagnosis of urinary tract infection (UTI). However, no one technique has become popular or widely used because of laborious procedures associated with the method. We investigated the usefulness of microscopic examination of uncentrifuged urine on disposable counting-chambers. A total of 89 urine samples were obtained from 53 children (24 male and 29 female). Urine samples were examined for bacteriuria and pyuria using a disposable counting chamber and its reliability was analyzed in predicting significant bacteriuria defined by routine urine culture. Significant bacteriuria was diagnosed in 23 of 89 urine samples by urine culture. Microscopic urine examination on disposable counting-chambers was very easy without the need to set up or wash chambers and provided immediate information. Urine bacterial concentration determined by the counting-chamber method was closely correlated to that determined by bacterial culture. The counting-chamber method identified bacteriuria correctly in 21 of 23 urine samples diagnosed as significant bacteriuria (sensitivity = 91%) and also gave a correct diagnosis of 64 of 66 urine samples with non-significant bacteriuria (specificity = 98%). Nineteen of the 23 urine samples with significant bacteriuria also had pyuria. The positive predictive value of concomitant bacteriuria and pyuria was 100%. When neither bacteriuria nor pyuria was found, the negative predictive value was 100%. It was concluded that urine microscopy using disposable counting chambers was very easy, inexpensive, quick and reliable and thus an extremely useful method for diagnosing UTI.

Diagnostic revolution of microhematuria by real time confocal scanning laser microscope: Hyodo-Iino-Miyagawa method, third report

The real time confocal scanning laser microscope provides excellent three-dimensional images free of out-of-focus information. The objective of this study was to evaluate the usefulness of the laser microscope for the diagnosis of microhematuria. Characteristics of the test were evaluated in 81 patients with definite causes of hematuria. 30 erythrocytes in urinary sediments were examined for each patient, and those in whom less than 20% of the erythrocytes were poikilocytes were considered to have urological diseases and those in whom 80% or more of the erythrocytes were poikilocytes to have nephritis. According to these criteria, the sensitivity and the specificity of the examination to nephritis were 100 and 98.1%. 91.4% of the patients with urological disease had the nonglomerular type. The time required for the examination was less than 2-5 min in samples containing 1-3 erythrocytes in one field under an ordinary light microscope (x400).

Strategies and criteria for developing new urinalysis tests

Urinalysis provides a non-invasive means to sequentially evaluate renal function and disease processes. Contemporary analytical techniques and the rapidly expanding knowledge of cell biology are yielding new ways of looking at urine constituents. Application of these new analytical techniques to screening, diagnosing and monitoring renal disease requires much more information than is currently available about the correlation of urine analytes with disease processes. Case definitions for specific renal disease depend upon a knowledge of natural history, response to therapy and laboratory data, including biopsy. When tests are being used to detect early stages of renal damage the subjects must be followed for months or years before a definitive diagnosis of irreversible disease can be established; therefore, prospective studies must be used to validate these tests. Analytes chosen for further study should be linked to significant renal pathophysiological processes. Gold standards for evaluating the predictive value of tests results must be established. The influence of renal disease on the analyte should be much greater than its biological variability under non-specific stresses. The results of using the test should benefit patients, taking into account the costs of false positive results and other costs to society that come from providing the test. Prospective studies needed to validate tests should be feasible and affordable. These studies could be facilitated by establishing a collaborative bank of urine samples linked to clinical data. Tests which are not used in clinical decision making are unimportant and of little value. Tests used in decision making should be evaluated as rigorously as the treatments that will be chosen based on the test results.

Evaluation of urine-based screening strategies to detect Chlamydia trachomatis among sexually active asymptomatic young males

OBJECTIVE

To evaluate the performances of diagnostic screening tests alone or in combination to detect asymptomatic chlamydial urethral infection in young males.

DESIGN

Comparisons of the performance profiles of the following chlamydia screening strategies were done: urethral culture; identification of polymorphonucleocytes (PMNs) on spun first-void urine (FVU); urinary leukocyte esterase test (LET) on unspun FVU; chlamydial enzyme immunoassay (EIA) applied to FVU sediment; combining LET on unspun FVU followed by EIA with or without direct fluorescent antibody (DFA) confirmation on FVU sediment; and combining PMNs on spun FVU followed by EIA with or without DFA confirmation.

SETTING

General clinics at a youth detention center, university-based teen clinic, college health service, and a military screening clinic.

PATIENTS

A total of 618 males aged 12 to 35 years (mean, 17 years) were recruited as a convenience sample; site participation rates ranged from 50% to 80%. Eligible subjects were sexually active, denied symptoms of urethritis, and had taken no antibiotics in the prior 2 weeks.

MAIN OUTCOME MEASURES

Sensitivity, specificity, and positive and negative predictive values of each test strategy's ability to detect Chlamydia trachomatis infection, and cost to confirm each positive case.

RESULTS

With a 7% prevalence of chlamydial infection, tissue culture had a sensitivity of only 61%. However, two strategies yielded significantly better performance profiles compared with the others: EIA confirmed by DFA test with a sensitivity of 84%, a specificity of 100%, and a cost to identify each positive case of $434; and PMNs followed by EIA confirmed by DFA test with a sensitivity of 78%, a specificity of 100%, and a cost to identify each positive case of $199. The LET followed by EIA-DFA had a similar performance profile to the PMN test strategies.

CONCLUSIONS

A combination of a nonspecific screening of FVU for PMNs or LET followed by specific testing with EIA with DFA confirmation has superior clinical and cost-effective performance for detecting asymptomatic C trachomatis urethritis in young males compared with other strategies. However, an evaluation of the medical, fiscal, and psychological benefits and risks associated with a specific screening strategy for sexually transmitted diseases must be made before adopting a specific strategy for a particular population.

A study of various tests to detect asymptomatic urinary tract infections in an obstetric population

OBJECTIVE

To compare rapid screening techniques for detecting asymptomatic urinary tract infections (AUTIs) in pregnant women.

DESIGN

Comparison of results of the screening tests of urinalysis, urine dipstick, and Gram's staining with the results of standard urine culture at an initial prenatal visit. In follow-up visits, urine dipstick testing was compared with urinalysis.

SETTING

Departments of Family Medicine and Obstetrics and Gynecology, Mayo Clinic, Rochester, Minn.

PATIENTS

Pregnant women (1047) from the local community were screened for AUTI on initial and follow-up visits.

METHODS

Initial prenatal urine was tested by using urine dipstick testing, urinalysis, Gram's staining, and urine culture. At each follow-up visit, urine specimens were tested by using urine dipstick and urinalysis.

MAIN OUTCOME MEASURES

Sensitivity and specificity, incremental patient costs, and clinical outcomes were used to assess the effectiveness of the techniques.

RESULTS

On initial visits, rapid screening tests for AUTI in pregnant women revealed the following: Gram's staining identified 22 of 24 patients with AUTI (sensitivity, 91.7%; specificity, 89.2%); urine dipstick, 12 of 24 (sensitivity, 50.0%; specificity, 96.9%); and urinalysis with presence of leukocytes, six of 24 (sensitivity, 25.0%; specificity, 99.0%). In follow-up visits, urine dipstick tests detected 19 infections and urinalysis, three (positive predictive value, 5% compared with 3%).

CONCLUSIONS

Urine dipstick testing for nitrites identified half of all patients with urinary tract infections and was superior to urinalysis on follow-up visits. Although Gram's staining is more expensive, it was more accurate for AUTI than urinalysis or urine dipstick test for nitrites. Urinalysis was never the test of choice because it was more expensive and detected fewer positive cultures. Leukocyte measurement correlated poorly with AUTI.

The case against screening urinalyses for asymptomatic bacteriuria in children

Screening children for asymptomatic bacteriuria to prevent pyelonephritis and renal scarring is widely recommended, but its cost-effectiveness has not been established. We reviewed published studies to determine the costs and benefits of screening toilet-trained, asymptomatic children for bacteriuria. Given the sensitivity and specificity of current screening methods (approximately 80% each) and the prevalence of bacteriuria in asymptomatic children (approximately 1% in girls and 0.03% in boys), screening 100,000 children would result in 19,897 (20%) false-positive tests; initial screening and two urine cultures to confirm the diagnosis of asymptomatic bacteriuria would miss 28% of 515 children with true bacteriuria, and cost nearly $2.9 million. There is no evidence that detection and treatment of children with asymptomatic bacteriuria prevents subsequent pyelonephritis or renal scarring. Screening for bacteriuria in asymptomatic children is costly, fails to prevent pyelonephritis or renal scarring, and should be discontinued as a part of routine well-child care.