Measurement of urinary leukocyte esterase activity: a screening test for urinary tract infections

What Is the Optimal Timing for Reading the Leukocyte Esterase Strip for the Diagnosis of Periprosthetic Joint Infection?

BACKGROUND

The leucocyte esterase (LE) strip test often is used to diagnose periprosthetic joint infection (PJI). In accordance with the manufacturer's directions, the LE strip test result is read 3 minutes after exposing it to joint fluid, but this has not been supported by robust research. Moreover, we have noted that the results of the LE strip test might change over time, and our previous studies have found that centrifugation causes the results of the LE strip test to degrade. Still, there is no evidence-based recommendation as to when to read the LE strip test to maximize diagnostic accuracy, in general, and the best reading times for the LE strip test before and after centrifugation need to be determined separately, in particular.

QUESTIONS/PURPOSES

(1) What is the optimal timing for reading LE strip test results before centrifugation to diagnose PJI? (2) What is the optimal timing for reading LE strip test results after centrifugation to diagnose PJI?

METHODS

This study was a prospective diagnostic trial. In all, 120 patients who were scheduled for revision arthroplasty and had signs of infection underwent joint aspiration in the outpatient operating room between July 2018 and July 2019 and were enrolled in this single-center study. For inclusion, patients must have had a diagnosis of PJI or nonPJI, valid synovial fluid samples, and must not have received antibiotics within 2 weeks before arthrocentesis. As such, 36 patients were excluded; 84 patients were included for analysis, and all 84 patients agreed to participate. The 2018 International Consensus Meeting Criteria (ICM 2018) was used for the classification of 49 patients with PJI (score ≥ 6) and 35 without PJI (score ≤ 2). The classification was used as the standard against which the different timings for reading LE strips were compared. All patients without PJI were followed for more than 1 year, during which they did not report the occurrence of PJI. All patients were graded against the diagnostic criteria regardless of their LE strip test results. In 83 patients, one drop of synovial fluid (50 μL) was applied to LE strips before and after centrifugation, and in one patient (without PJI), the sample was not centrifuged because the sample volume was less than 1.5 mL. The results of the strip test were read on an automated colorimeter. Starting from 1 minute after centrifugation, these strips were automatically read once every minute, 15 times (over a period of 16 minutes), and the results were independently recorded by two observers. Results were rated as negative, ±, 1+, and 2+ upon the machine reading. Grade 2+ (dark purple) was used as the threshold for a positive result. An investigator who was blinded to the study performed the statistics. Optimal timing for reading the LE strip before and after centrifugation was determined by using receiver operative characteristic (ROC) analysis. The specificity, sensitivity, and positive predictive and negative predictive values were calculated for key timepoints.

RESULTS

Before centrifugation, the area under the curve was the highest when the results were read at 5 minutes (0.90 [95% CI 0.83 to 0.98]; sensitivity 0.88 [95% CI 0.75 to 0.95]; specificity 0.89 [95% CI 0.72 to 0.96]). After centrifugation, the area under the curve was the highest when the results were read at 10 minutes (0.92 [95% CI 0.86 to 0.98]; sensitivity 0.65 [95% CI 0.50 to 0.78]; specificity 0.97 [95% CI 0.83 to 1.00]).

CONCLUSION

The LE strip test results are affected by time and centrifugation. For samples without centrifugation, we found that 5 minutes after application was the best time to read LE strips. We cannot deny the use of centrifuges because this is an effective way to solve the sample-mingling problem at present. We recommend 10 minutes postapplication as the most appropriate time to read LE strips after centrifugation. Multicenter and large-sample size studies are warranted to further verify our conclusion.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Promising Roles of Alternative Medicine and Plant-Based Nanotechnology as Remedies for Urinary Tract Infections

Urinary tract infections (UTIs) are considered to be the most common infections worldwide, having an incidence rate of 40-60% in women. Moreover, the prevalence of this disorder in adult women is 30 times more than in men. UTIs are usually found in many hospitals and clinical practice; as disorders, they are complicated and uncomplicated; in uncomplicated cases, there is no structural or functional abnormality in the urogenital tract. However, obstruction, retention of urine flow and use of catheters increase the complexity. There are several bacteria (e.g., E. coli, Klebsiella pneumoniae, Proteus vulgaris, etc.) successfully residing in the tract. The diagnosis must not only be accurate but rapid, so early detection is an important step in the control of UTIs caused by uropathogens. The treatment of UTIs includes appropriate antimicrobial therapy to control the infection and kill the causal microbes inside the body. A long-time usage of antibiotics has resulted in multidrug resistance causing an impediment in treatment. Thus, alternative, combinatorial medication approaches have given some hope. Available treatments considered Homeopathic, Ayurvedic, Unani, and other herbal-based drugs. There are new upcoming roles of nanoparticles in combating UTIs which needs further validation. The role of medicinal plant-based nanotechnology approaches has shown promising results. Therefore, there must be active research in phyto-based therapies of UTIs, such as Ayurvedic Biology.

Activity-based Protein Profiling Approaches for Transplantation

Enzyme activity may be more pathophysiologically relevant than enzyme quantity and is regulated by changes in conformational status that are undetectable by traditional proteomic approaches. Further, enzyme activity may provide insights into rapid physiological responses to inflammation/injury that are not dependent on de novo protein transcription. Activity-based protein profiling (ABPP) is a chemical proteomic approach designed to characterize and identify active enzymes within complex biological samples. Activity probes have been developed to interrogate multiple enzyme families with broad applicability, including but not limited to serine hydrolases, cysteine proteases, matrix metalloproteases, nitrilases, caspases, and histone deacetylases. The goal of this overview is to describe the overall rationale, approach, methods, challenges, and potential applications of ABPP to transplantation research. To do so, we present a case example of urine serine hydrolase ABPP in kidney transplant rejection to illustrate the utility and workflow of this analytical approach. Ultimately, developing novel transplant therapeutics is critically dependent on understanding the pathophysiological processes that result in loss of transplant function. ABPP offers a new dimension for characterizing dynamic changes in clinical samples. The capacity to identify and measure relevant enzyme activities provides fresh opportunities for understanding these processes and may help identify markers of disease activity for the development of novel diagnostics and real-time monitoring of patients. Finally, these insights into enzyme activity may also help to identify new transplant therapeutics, such as enzyme-specific inhibitors.

Electroanalysis of Infection with Methyl Pyruvate

The discovery of infection enzyme leukocyte esterase (LE) hydrolyzing a mitochondrial substrate methyl pyruvate (MP) was explored in the development of electroanalytical methods for LE in human biofluids. The LE + MP reaction was coupled with alcohol oxidase to produce hydrogen peroxide, which was then reduced at a nitrogen-doped carbon nanotube electrode at -0.20 V, yielding current proportional to the LE content in a sample. The kinetic assays revealed a fast turnover (k_cat = 15 s^-1) and high specificity constant (k_catK_m^-1 = 2.3 × 10⁶ M^-1 s^-1) for the LE-triggered hydrolysis of MP. The analytical assays were short (5 min) and the quantified LE was in the clinically relevant range of 22-300 μg L^-1 (R², 0.985). The immuno-electroanalysis could detect the picomole quantity of LE and yielded linear calibration plots up to 150 μg L^-1 of LE with the same slope regardless of the sample matrix (urine, saliva, and phosphate buffer). The spike-and-recovery experiments displayed an LE recovery of 99-104%. The amperometric immunoassay of LE was less laborious than traditional enzyme-linked immunosorbent assay (ELISA) for LE and reduced the required sample incubation time from 4 h (sandwich ELISA) to 30 min (immuno-electroanalysis). The proposed combination of immunosorption with internally calibrated amperometry can also be used for a selective determination of other enzymes, which form enzymatically active immune complexes.

Useful Predictive Factors for Bacteremia among Outpatients with Pyelonephritis

Objective The aim of this study was to identify predictive factors for bacteremia conveniently and quickly among outpatients diagnosed with pyelonephritis. Patients All patients who were diagnosed with pyelonephritis at the outpatient clinic in the Department of General Medicine of Juntendo University Hospital from April 1, 2008, to June 30, 2015, were enrolled. Patients from whom blood cultures had not been taken were excluded. Methods Clinical information was extracted from medical charts. Factors potentially predictive of bacteremia were analyzed using a t-test and Fisher's exact test, followed by a multivariable logistic regression model analysis. Results Blood cultures were drawn from 116 patients, and 25 (22%) presented with bacteremia. A multivariate analysis with the age, chills, platelet count and urine nitrite test results revealed that older age, positive urinary nitrite test results and chills tended to be associated with bacteremia, respectively. [older age: unit odds ratio (OR) 1.02, p=0.052, 95% confidence interval (CI) 1.00-1.05, positive urinary nitrite test findings: OR 2.5, p=0.092, 95% CI 0.86-7.7, chills: OR 2.5, p=0.096, 95% CI 0.84-7.65]. The area under the receiver operating characteristic (ROC) curve of this model was 0.77. Regardless of age, positive urinary nitrite test findings were significantly associated with bacteremia (OR 3.1, p=0.033, 95% CI 1.1-9.2), and chills tended to be associated with bacteremia (OR 2.7, p=0.07, 95% CI 0.93-7.9) The area under the ROC curve of this model was 0.75. Conclusion Bacteremia should be considered in pyelonephritis patients with rapidly assessable factors in outpatient clinic. In particular, a model including a urinary nitrite test has the potential to aid in the prediction of bacteremia.

Effect of Depth of Centrifuged Synovial Fluid on Leukocyte Esterase Test for Periprosthetic Joint Infection

Centrifugation of aspirated synovial fluid before leukocytes esterase (LE) testing for diagnosing periprosthetic joint infection (PJI) may make blood tinged specimens interpretable. We aimed to establish the proper sampling depth of centrifuged specimens for LE testing as one diagnostic criterion and also AS-D chloroacetate esterase (CAE) staining testing as an adjunctive tool. A definite PJI knee joint group and an aseptic primary total knee arthroplasty control group were studied quasi-experimentally (N = 46). At 2,000 g for 15 min, 3 ml of synovial fluid was centrifuged. LE strip testing and median synovial WBC count were performed at 2, 4, and 6 mm depths. CAE staining test characterized LE particles. ROC curve, area under the curve, and significant differences were determined. The proper predictive depth to diagnose PJI was sought by forward stepwise logistic regression. All fresh blood-tinged specimens had uncertain interpretations. Centrifugation increased interpretability (55-100%). ROC curve and area under the curve at 2, 4, and 6 mm depths were 0.822, 0.804, and 0.786, respectively. The cut point of ++ to diagnose PJI was statistically significant (p < 0.05) at all depths. p-values of forward stepwise logistic regression at 2, 4, and 6 mm were 0.001, 0.752, and 0.756, respectively. CAE staining confirmed extracellular LE release by polymorphonuclear neutrophils (PMN). A specimen at <2 mm from the surface of centrifuged synovial fluid at a grading of ++ or more for PJI diagnosis is proper for LE testing. CAE staining testing adjunctively characterizes LE particles and cell morphology. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2545-2550, 2017.

Comparison of Leukocyte Esterase Testing of Synovial Fluid with Synovial Histology for the Diagnosis of Periprosthetic Joint Infection

Background

Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty (TJA). The leukocyte esterase (LE) strip test and histology are diagnostic methods for PJI. The aims of this study were to determine the sensitivity and specificity of the LE strip test and to compare it with histology in the diagnosis of PJI.

Material/Methods

Between January and December 2015, 93 patients who underwent TJA with PJI were enrolled in the study. Synovial fluid samples were tested with an LE strip, and three synovial tissue samples from each patient underwent frozen section and formalin-fixed histology. Recent criteria from the Musculoskeletal Infection Society (MSIS) were used for the diagnosis of PJI.

Results

Ninety-three patients studied included 38 cases of PJI and 55 non-infected cases. Sensitivity and specificity of the LE strip test were 92.1% (95% CI, 77.5–97.9%) and 96.4% (95% CI, 86.4–99.4%), respectively. There was no significant difference in sensitivity (p=0.249) or specificity (p=0.480) between frozen and paraffin sections for histology; the two methods were strongly correlated (ϕ=0.892). Comparison of the LE test results with histology showed a strong correlation (ϕ=0.758, and ϕ=0.840).

Conclusions

The findings of this preliminary study have shown that the LE strip test on synovial fluid showed similar sensitivity and specificity as histology for the diagnosis of PJI, indicating that that further controlled clinical studies should be performed to investigate the role of the LE strip test for the early diagnosis of PJI.

Effectiveness of leucocyte esterase as a diagnostic test for acute septic arthritis

BACKGROUND

We hypothesized that leucocyte esterase strip test can aid in diagnosing septic arthritis in native synovial fluid because leucocyte esterase concentrations would be elevated at the infection site because of secretion by recruited neutrophils.

METHOD

The cohort included 27 patients (suspected septic arthritis and normal subjects). A standard chemical test strip (graded as negative, trace, +, ++ or +++) was used to detect the presence of leucocyte esterase. Fluid leucocyte count, Gram staining, culture, erythrocyte sedimentation rate and C-reactive protein were also assessed.

RESULTS

The leucocyte esterase test with a threshold of ++/+++ had a sensitivity of 79.2% (95% CI [confidence interval], 65.9% to 89.2%), specificity of 80.8% (95% CI, 73.3% to 87.1%), positive predictive value (PPV) of 61.8% (95% CI, 49.2% to 73.3%) and negative predictive value (NPV) of 90.1% (95% CI, 84.3% to 95.4%).

CONCLUSION

The leucocyte esterase strip test yielded a high specificity, PPV, NPV, high sensitivity and high diagnostic accuracy. Leucocyte esterase is an accurate, quick and bedside test for septic arthritis and can be used effectively for diagnosing periprosthetic joint infections along with other battery of tests according to the Musculoskeletal Infection Society criteria.

Use of leucocyte esterase reagent strips in the diagnosis or exclusion of prosthetic joint infection

Infection is a leading indication for revision arthroplasty. Established criteria used to diagnose prosthetic joint infection (PJI) include a range of laboratory tests. Leucocyte esterase (LE) is widely used on a colorimetric reagent strip for the diagnosis of urinary tract infections. This inexpensive test may be used for the diagnosis or exclusion of PJI. Aspirates from 30 total hip arthroplasties (THAs) and 79 knee arthroplasties (KA) were analysed for LE activity. Semi-quantitative reagent strip readings of 15, 70, 125 and 500 white blood cells (WBC) were validated against a manual synovial white cell count (WCC). A receiver operating characteristic (ROC) curve was constructed to determine the optimal cut-off point for the semi-quantitative results. Based on established criteria, six THAs and 15 KAs were classified as infected. The optimal cut-off point for the diagnosis of PJI was 97 WBC. The closest semi-quantitative reading for a positive result was 125 WBC, achieving a sensitivity of 81% and a specificity of 93%. The positive and negative predictive values of the LE test strip were 74% and 95% respectively.

The LE reagent strip had a high specificity and negative predictive value. A negative result may exclude PJI and negate the need for further diagnostic tests.

Cite this article: Bone Joint J 2015;97-B:1232–6.

Diagnosis of periprosthetic joint infection: the utility of a simple yet unappreciated enzyme

BACKGROUND

The white blood-cell count and neutrophil differential of the synovial fluid have been reported to have high sensitivity and specificity in the diagnosis of periprosthetic infection following total knee arthroplasty. We hypothesized that neutrophils recruited into an infected joint secrete enzymes that may be used as markers for infection. In this prospective study, we determined the sensitivity and specificity of one of these enzymes, leukocyte esterase, in diagnosing periprosthetic joint infection.

METHODS

Between May 2007 and April 2010, synovial fluid was obtained preoperatively from the knees of patients with a possible joint infection and intraoperatively from the knees of patients undergoing revision knee arthroplasty. The aspirate was tested for the presence of leukocyte esterase with use of a simple colorimetric strip test. The color change (graded as negative, trace, +, or ++), which corresponded to the level of the enzyme, was noted after one or two minutes.

RESULTS

On the basis of clinical, serological, and operative criteria, thirty of the 108 knees undergoing revision arthroplasty were infected and seventy-eight were uninfected. When only a ++ reading was considered positive, the leukocyte esterase test was 80.6% sensitive (95% confidence interval [CI], 61.9% to 91.9%) and 100% specific (95% CI, 94.5% to 100.0%), with a positive predictive value of 100% (95% CI, 83.4% to 100.0%) and a negative predictive value of 93.3% (95% CI, 85.4% to 97.2%). The leukocyte esterase level correlated strongly with the percentage of polymorphonuclear leukocytes (r = 0.7769) and total white blood-cell count (r = 0.5024) in the aspirate as well as with the erythrocyte sedimentation rate (r = 0.6188) and C-reactive protein level (r = 0.4719) in the serum.

CONCLUSIONS

The simple colorimetric strip test that detects the presence of leukocyte esterase in synovial fluid appears to be an extremely valuable addition to the physician's armamentarium for the diagnosis of periprosthetic joint infection. The leukocyte esterase reagent strip has the advantages of providing real-time results, being simple and inexpensive, and having the ability to both rule out and confirm periprosthetic joint infection. However, additional multicenter studies are required to substantiate the results of our preliminary investigation before the reagent strip can be used confidently in the clinic or intraoperative setting.

Molecular markers for diagnosis of periprosthetic joint infection

Despite a battery of tests available for diagnosing periprosthetic joint infection, as yet, no gold standard has been identified. Our purpose was to measure inflammatory proteins in synovial fluid from patients undergoing revision arthroplasty for septic or aseptic failure. We analyzed 74 synovial fluid samples: 31 infected and 43 uninfected, based on clinical and laboratory criteria. Proteomics analysis and receiver operating characteristic curve analyses were conducted on 46 inflammatory proteins for each sample. Of 46 proteins, 5 (interleukin 6, interleukin 8, α(2)-macroglobulin, C-reactive protein, and vascular endothelial growth factor) had an area under the curve greater than 0.90. This prospective study has demonstrated promising results for the use of molecular markers in diagnosis of periprosthetic joint infection. Future studies will focus on designing assays with these proteins in mind.

The use of urinary dipstick tests to exclude urinary tract infection: a systematic review of the literature

Several systematic reviews have examined the use of dipstick tests to diagnose or rule in urinary tract infection (UTI). We examined the evidence relating to the use of urine leukocyte esterase and nitrite tests in adults to exclude or rule out UTI. A search of the literature from 1966 to 2003 revealed 30 studies as containing relevant and suitable information and 23 of these, which used a cut-off of 108 colony-forming units per liter, were combined in a meta-analysis. The leukocyte esterase or nitrite test combination, with one or the other test positive, was used in 14 studies, showed the highest sensitivity and the lowest negative likelihood ratio. While there was significant heterogeneity between the studies, 7 of 14 demonstrated significant decreases in pretest to posttest probability with a pooled posttest probability of 5% for the negative result. In certain circumstances, there is evidence for the use of urinalysis as a rule-out test for UTI.

All dysuria is local. A cost-effectiveness model for designing site-specific management algorithms

OBJECTIVE

To determine the cost-effectiveness of management strategies for dysuria in different office settings.

DESIGN

Decision and cost-effectiveness analyses, assuming the payer's perspective. Data on disease prevalence, test characteristics, treatment efficacy, and adverse effects were drawn from the English language literature using medline searches and bibliographies.

SETTING

Hypothetical primary care practice.

PATIENTS

Otherwise healthy, nonpregnant women with symptoms of dysuria, urgency, and frequency.

INTERVENTIONS

All reasonable combinations of urinalysis, urine culture, pelvic examination, chlamydia and gonorrhea cultures, and empiric treatment with trimethoprim-sulfamethoxazole.

RESULTS

The cost-effectiveness of strategies varied substantially among different patient settings. In all settings, empiric trimethoprim-sulfamethoxazole for all patients was least expensive and least effective. Most testing increased both cost and effectiveness. Compared to empiric antibiotics, performing pelvic examination and urine culture for women with normal urinalyses had a marginal cost-effectiveness ratio of $4 to $32 per symptom-day avoided (SDA). Adding urine culture for patients with pyuria had a marginal cost of $34 to $107 per SDA, which fell to $40/SDA when the prevalence of resistance to trimethoprim-sulfamethoxazole exceeded 40%. Pelvic examination and urine culture for all patients regardless of urinalysis results achieved the greatest benefit but at the highest cost (>$300 per SDA).

CONCLUSIONS

In otherwise healthy women with symptoms of dysuria and no vaginal complaints, performing pelvic exam and urine culture based on urinalysis offers a reasonable alternative to empiric therapy. Other testing may be warranted, depending on antibiotic resistance and the value of avoiding a day of dysuria.

Urinary tract infections in the critically ill patient with a urinary catheter

BACKGROUND

The diagnosis of urosepsis should be entertained each time a patient has a febrile episode. Urosepsis carries with it a mortality rate of 25% to 60%. We determined the incidence and risk factors of urosepsis in the catheterized critically ill patient.

MATERIALS AND METHODS

The charts of 142 subjects admitted from November 1994 to November 1995 to the trauma intensive care units at our institution with a urinary catheter were reviewed. Urosepsis was defined as (1) positive blood and urine cultures that correlated; (2) positive urine cultures with radiologic evidence of obstructive uropathy or infection; or (3) positive urine cultures and all other cultures negative to be eligible for the urosepsis group.

RESULTS

Of the 126 patients evaluated for sepsis, 20 (15.8%) were diagnosed with urosepsis. Multivariant analysis demonstrated that the incidence of urosepsis was correlated with the following: age >60 years, extended length of stay in the intensive care unit and/or hospital, and duration of urinary catheterization. All 20 patients who developed urosepsis had a positive urinalysis and a positive urine culture (sensitivity 100%). However, urinalyses were positive in another 63 patients who did not have urosepsis (specificity 24.1%), and urine cultures were positive in 31 patients who did not have urosepsis (specificity 70.8%).

CONCLUSION

We found a 15.8% incidence of urosepsis in our patient population. Urosepsis was more likely to occur in patients over 60 years of age, patients with extended length of stay in the intensive care unit or in the hospital in general, and patients with an extended duration of urinary catheterization.

A predictive model to estimate the risk of serious bacterial infections in febrile infants

Low risk criteria have been defined to identify febrile infants unlikely to have serious bacterial infection (SBI). Using these criteria approximately 40% of all febrile infants can be defined as being at low risk. Of the remaining infants (60%) only 10%-20% have an SBI. No adequate criteria exist to identify these infants. All infants aged 2 weeks-1 year, presenting during a 1-year-period with rectal temperature > or = 38.0 degrees C to the Sophia Children's Hospital were included in a prospective study. Infants with a history of prematurity, perinatal complications, known underlying disease, antibiotic treatment or vaccination during the preceding 48 h were excluded. Clinical and laboratory variables at presentation were evaluated by a multivariate logistic regression model using SBI as the dependent variable. By using likelihood ratios a predictive model was derived, providing a post test probability of SBI for every individual patient. Of the 138 infants included in the study, 33 (24%) had SBI. Logistic regression analysis defined C-reactive protein (CRP), duration of fever, standardized clinical impression score, a history of diarrhoea and focal signs of infection as independent predictors of SBI.

CONCLUSION

CRP, duration of fever, the "standardized clinical impression score", a history of diarrhoea and focal signs of infection were the independent, most powerful predictors of SBI in febrile infants, identified by logistic regression analysis. Although the predictive model is not validated for direct clinical use, it illustrates the clinical potential of the used technique. This technique offers the advantage of assess the probability of SBI in every individual infant. This probability will form the best basis for well-founded decisions in the management of the individual febrile infant.

Rapid dipstick test for diagnosis of urinary tract infection

The rapid dipstick test of urine leukocyte esterase (LE) activity and nitrite has not been studied fully in pediatric clinical situations. We investigated the usefulness of the dipstick LE and nitrite test in the screening of urinary tract infection (UTI) in pediatric patients. Ninety-two fresh urine samples were obtained from children suspected of having UTI. Leukocyte esterase activity and nitrite were measured in the urine specimens read by a photometer. Leukocytes were also counted on a disposable slide. Urine samples were examined for bacteriuria by the standard culture method. The results of the urine dipstick test of LE showed a close relationship with leukocyte counts on a counting chamber. Leukocyte esterase (-) indicated leukocyte counts of less than 10/uL with a probability of 97% (58/60). Of the 22 urine samples with significant bacteriuria diagnosed by standard urine culture, the nitrite test did not detect bacteriuria in 10. While the sensitivities of the dipstick tests of nitrite (+) and LE +/- or more for the diagnosis of significant bacteriuria were 55% (12/22) and 86% (19/22), respectively, the sensitivity and negative predictive value of the combined test were 100%. These results suggest that use of the dipstick test of LE and nitrite can avoid a large part of the cost incurred by urine culture and is useful for screening UTI in children.

Evaluation of bedside testing options for the critical care unit

Bedside testing offers a unique opportunity for earlier and more specific diagnosis, faster and more frequent monitoring, and the opportunity to improve patient care and reduce hospital costs. However, if abused it may not improve patient care and may increase hospital costs. In the future, more clinical studies will need to be performed to determine which tests are cost-effective.

The leukocyte esterase test for detection of cerebrospinal fluid leukocytosis and bacterial meningitis

We conducted a study to assess the efficacy of the dipstick leukocyte esterase test (LET) in the detection of cerebrospinal fluid (CSF) leukocytosis as a quick screen for bacterial meningitis. Nine hundred forty-two CSF samples were collected from 800 patients. The LET was compared in a double-blinded fashion with routine cell count determinations and cultures. We reviewed the clinical courses of all patients with positive cultures to assess the significance of culture isolates. Statistical analysis revealed LET sensitivity of 84.4% and specificity of 98.1% for clinical presentations of bacterial meningitis for which initiation of therapy is currently recommended. The LET identified culture-proven cases of meningitis with sensitivity of 73% and specificity of 95%. We propose the LET as an adjunct to, but not a replacement for, CSF cell count and chemistry determination in the initial laboratory assessment of bacterial meningitis. It is a reasonable screen that allows rapid initiation of treatment and directs the laboratory technician to devote extra attention to examination of a CSF specimen with a higher likelihood of pathology.

Bedside analysis of arterial blood gases and electrolytes during and after cardiac surgery

Intraoperative changes in arterial blood gas tensions and serum electrolyte concentrations may contribute to the development of arrhythmias and cardiovascular insufficiency. Rapid intraoperative assessment of these parameters may improve patient care by permitting earlier treatment of abnormalities. We evaluated a portable blood gas and electrolyte analyzer in six patients undergoing coronary artery bypass surgery. Evaluation by anesthesia personnel took place in the operating room. The analyzer produced rapid, accurate, and reliable data that were comparable to clinical laboratory data. Correlation coefficients between the analyzer and laboratory determinations for PaO2, PaCO2, pH, K+, Ca++, and hematocrit were all greater than 0.92. Large changes in circulating ionized calcium (18%) and potassium (38%) concentrations were noted during cardiac surgery. Bedside blood gas and electrolyte analyzers represent a new technology worthy of further evaluation.

A simple spectrophotometric assay for urinary leukocyte esterase activity

We have developed a sensitive spectrophotometric method for assaying urinary leukocyte esterase activity by employing a synthetic substrate, N-toluene sulfonyl indoxyl alanine ester. This kinetic assay can be performed with a small aliquot of urine, by following the change in absorbance of the chromophore at 385 nm. It is rapid and specific for leukocyte esterase and therefore can be used in the early diagnosis of urinary tract infection.

Leukocyte esterase activity in human amniotic fluid for the rapid detection of chorioamnionitis

Chorioamnionitis plays an important role in perinatal morbidity and mortality. Fast and accurate diagnosis poses a major problem. A prospective study was performed to assess the value of positive leukocyte esterase test (Chemstrip 9) for the diagnosis of chorioamnionitis during labor. We evaluated 21 patients with chorioamnionitis in labor at term and used 21 matched control subjects. The sensitivity and specificity of leukocyte esterase activity were compared with those of amniotic fluid cultures, Gram stains, maternal pyrexia and leukocytosis, and fetal tachycardia. The sensitivity in diagnosing chorioamnionitis was 91% and the specificity was 95%. The use of this test strip could provide a rapid, inexpensive screening test for chorioamnionitis.

The urinalysis: a critical appraisal

The urinalysis, an inexpensive office test, is often performed unnecessarily. Improved chemical testing using reagent strips obviates the need for routine microscopy in many cases. More information is needed to make specific recommendations on the use of the routine urinalysis as a screening procedure.

Pharmacologic management of the critically ill patient in the perioperative period--emphasis on the sepsis syndrome

The critically ill perioperative patient requires complex pharmacologic management. The ability to measure circulating drug concentrations has helped the clinician to properly modulate therapy, especially with potentially toxic agents. Postoperative sepsis remains a difficult therapeutic problem. Controversial therapies, such as the use of corticosteroids and the utility of newer pharmacologic approaches, are beginning to be properly tested in multicenter trials. Improvements in technology (e.g., development of monoclonal antibodies), biochemistry, and pharmacology have resulted in the development of exciting, new pharmacologic avenues for the management of the critically ill perioperative patient.

The usefulness of screening tests for pyuria in combination with culture in the diagnosis of urinary tract infection

A prospective study was conducted to examine the usefulness of screening tests for pyuria in combination with culture in the diagnosis of urinary tract infection (UTI) in outpatients. Midstream urine specimens were collected from 340 patients seen in the emergency treatment center (ETC) and were examined for pyuria using the chamber count method and the Leukocyte Esterase Dipstick test (LE; Bio Dynamics, Indianapolis, IN). All specimens were cultured quantitatively using both 0.01 ml and 0.001 ml calibrated bacteriologic loops. A total of 100 UTIs, defined by combined clinical and laboratory critera, were identified. Sixty-four (64%) infections were identified by culture using the standard interpretive breakpoint of greater than or equal to 10(5) CFU/ml and an additional 36 (36%) were detected using the low-count interpretive breakpoint of greater than or equal to 10(3) CFU/ml. We found pyuria detection by either the chamber count method or the LE test to be extremely useful in directing subsequent culture efforts. By using either of the tests for pyuria to determine the significance of low-count bacteriuria (10(3) - less than 10(5) CFU/ml) we were able to achieve maximum sensitivity (92%-99%) and specificity (99.2-99.6%) for the diagnosis of UTI while minimizing the number of specimens in which low numbers of organisms must be evaluated.

Utility of urine cultures in the emergency department

Urinary tract infection (UTI) is a common problem treated by emergency physicians. A midstream urine sample remains the most frequent method of culture collection. Although midstream urine culture growing more than 10(5) colony-forming units per milliliter (cfu/mL) has been considered diagnostic of UTI, high false-positive and false-negative rates as well as a lack of precision have been associated with this method of collection. Alternative methods of establishing the diagnosis of UTI have excellent sensitivity and may be utilized at the time of patient presentation. These include the detection of leukocyte esterase activity in urine and the presence of one or more bacteria on microscopic examination of an unspun urine sample. Women of child-bearing age represent the vast majority of patients seen with UTI. Uncomplicated infection of the urinary tract has a generally benign course in these patients, and is rarely associated with long-term complications. In addition, these patients are infected with a predictable spectrum of uropathogens that respond to the commonly used antibiotics. It appears that urine cultures provide little additional information in this patient population. Urine cultures should be obtained in patients at high risk for pyelonephritis or bacteremia/urosepsis, as well as in those expected to have uncommon or resistant organisms.

Improved urine screening using a combination of leukocyte esterase and the Lumac system

Three rapid urine screening tests, leukocyte esterase, nitrite, and the Lumac System for detection of bacterial ATP, were evaluated alone and in combination to determine their utility in screening urine specimens from male patients for bacteruria. The combination of leukocyte esterase and Lumac testing resulted in significant improvement in the sensitivity of urine screening over each test individually and the combination of leukocyte esterase and nitrite. The leukocyte esterase/Lumac combination detected 98% of those specimens with greater than or equal to 10(5) CFU/ml and had a negative predictive value of 99%. The results obtained from this type of testing can be used with confidence to minimize the number of urine specimens cultured and to provide rapid reporting of negative results.

Use of rapid screening tests in processing urine specimens by conventional culture and the AutoMicrobic system

Two rapid urine screening tests, the Chemstrip LN (BioDynamics, Indianapolis, Ind.) and the Bac-T-Screen urine screening device (Marion Laboratories, Inc., Kansas City, Mo.), were evaluated as techniques to predict bacteriuria as quantitated by either conventional culture or the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.). A total of 666 urine specimens were analyzed by both screening tests as well as the AutoMicrobic system and quantitative culture. The sensitivities of both Chemstrip LN and Bac-T-Screen for the detection of low levels of bacteriuria (greater than or equal to 10(3) CFU/ml) were comparable (73.3 and 74.4%, respectively) and were too low to recommend their use as a primary urine screen. Their excellent predictive value of a negative result at the 10(5) CFU/ml level (96 and 97.5%, respectively) makes them potentially useful in predicting urine specimens with less than 10(5) CFU/ml. The use of either of these tests in combination with the AutoMicrobic system markedly decreased the time required to classify urine specimens. Their low cost relative to the AutoMicrobic system urine card makes the use of either test cost effective as a screen for the AutoMicrobic system.

Laboratory evaluation of leukocyte esterase and nitrite tests for the detection of bacteriuria

We compared the sensitivity, specificity, and predictive values of the 1-min leukocyte esterase test and the test for urinary nitrite alone and in combination as screening tests for bacteriuria in over 5,000 clinical urine specimens. The leukocyte esterase-nitrite combination had a sensitivity of 79.2%, a specificity of 81%, and a negative predictive value of a negative test of 94.5% for specimens with greater than or equal to 10(5) CFU/ml. Although the sensitivity of this test was too low to allow its use as the only screening test for bacteriuria, it may serve as a useful adjunct to culturing and other urine-processing systems in the microbiology laboratory.