Bedside leucocyte esterase reagent strips with spectrophotometric analysis to rapidly exclude spontaneous bacterial peritonitis: a pilot study

Performance of Leukocyte Esterase Reagent Strips in the Detection of Spontaneous Bacterial Peritonitis in Cirrhotic Patients: A Systematic Review and Meta-analysis

Background

Spontaneous bacterial peritonitis (SBP) is a bacterial infection associated with a high mortality rate in cirrhotic patients. The gold standard for the detection of SBP is a manual cell count from ascitic fluid; however, alternative screening methods are under investigation. In particular, leukocyte esterase reagent strips (LERS) has been studied as an alternative method to detect SBP with a low cost and instant turnaround time. Therefore, this study aims to evaluate the performance of LERS in the detection of SBP.

Methods

A literature search was performed for studies evaluating LERS for the detection of SBP on PubMed, Embase, Scopus, Cochrane, and clinical trial registries. Summary sensitivity, specificity, log diagnostic odds ratio (LDOR), and the area under the summary receiver operating curve (AUC) were calculated according to the respective manufacturer.

Results

In total, 31 studies were evaluated. The summary sensitivity of Aution Sticks, Combur, Multistix, Periscreen reagent strips was 0.962 (95% confidence interval [CI] 0.926, 0.998), 0.892 (95% CI 0.846, 0.938), 0.806 (95% CI 0.738, 0.874), and 0.939 (95% CI 0.900, 0.979), respectively. The summary specificity of Aution Sticks, Combur, Multistix, and Periscreen reagent strips was 0.940 (95% CI 0.904, 0.976), 0.922 (95% CI 0.874, 0.970), 0.974 (95% CI 0.962, 0.985), and 0.672 (95% CI 0.381, 0.963), respectively.

Conclusion

LERS appears to have a notable overall performance for the detection of SBP. LERS appeared to be an acceptable alternative to diagnose SBP in facilities without ability to perform cell count. However, there were significant differences in performance between each manufacturer.

Measurement of calprotectin in ascitic fluid to identify elevated polymorphonuclear cell count

AIM: To evaluate the diagnostic capability of calprotectin in ascitic fluid for detecting a polymorphonuclear (PMN) cell count > 250/μL ascites.

METHODS: In this prospective observational study, a total of 130 ascites samples were analysed from 71 consecutive patients referred for paracentesis. Total and differential leukocyte cell counts were determined manually with a Neubauer chamber and gentian-violet stain. Calprotectin was measured in 1 mL ascetic fluid by enzyme-linked immunosorbent assay (ELISA) and a point-of-care (POC) lateral flow assay with the Quantum Blue^® Reader (Bühlmann Laboratories). All measurements were carried out in a central laboratory by senior personnel blinded to patient history. A PMN count > 250/μL was the primary endpoint of the study. The diagnostic value of ascitic calprotectin measurement was assessed by comparing to the final diagnosis of each patient that had been adjudicated by investigators blinded to calprotectin values.

RESULTS: The PMN count was > 250/μL in 19 samples (14.6%) from 15 patients (21.1%) and varied widely among the study population (range 10-19 800/mL and 1-17 820/mL, respectively). Spontaneous bacterial peritonitis (SBP) was the final diagnosis in four patients (5.6%). All patients with PMN ≤ 250/μL had negative bacterial culture. PMN count was elevated in five patients with peritoneal carcinomatosis, three with lymphoma, one with neuroendocrine carcinoma, and two with secondary peritonitis due to abdominal perforation. PMN cell counts correlated with ascitic calprotectin values (Spearman’s rho; r = 0.457 for ELISA, r = 0.473 for POC). A considerable range of ascitic calprotectin concentrations was detected by ELISA [median 0.43 μg/mL, interquartile range (IQR) 0.23-1.23 (range 0.10-14.93)] and POC [median 0.38 μg/mL, IQR 0.38-0.56 (range 0.38-13.31)]. Ascitic calprotectin levels were higher in samples with PMN > 250/μL, by both ELISA [median (IQR) 2.48 μg/mL (1.61-3.65) vs 0.10 μg/mL (0.10-0.36), P < 0.001] and POC [2.78 μg/mL (2.05-5.37) vs 0.38 μg/mL (0.38-0.41), P < 0.001]. The area under the receiver operating characteristics curve for identifying an elevated PMN count was 0.977 (95%CI: 0.933 to 0.995) for ELISA and 0.982 (95%CI: 0.942 to 0.997) for POC (P = 0.246 vs ELISA). Using the optimal cut-off value for ELISA (0.63 μg/mL), ascitic calprotectin had 94.8% sensitivity, 89.2% specificity, positive and negative likelihood ratios of 8.76 and 0.06 respectively, positive and negative predictive values of 60.0% and 99.0% respectively, and 90.0% overall accuracy. Using the optimal cut-off value for POC (0.51 μg/mL), the respective values were 100.0%, 84.7%, 6.53, 0.00, 52.8%, 100% and 87.7%. Correlation between ELISA and POC was excellent (r = 0.873, P < 0.001). The mean ± SD of the difference was -0.11 ± 0.48 μg/mL with limits of agreement of + 0.8 μg/mL (95%CI: 0.69 to 0.98) and -1.1 μg/mL (95%CI: -1.19 to -0.91).

CONCLUSION: Ascitic calprotectin reliably predicts PMN count > 250/μL, which may prove useful in the diagnosis of SBP, especially with a readily available bedside testing device.

Multistix 10 SG Leukocyte Esterage Dipstick Testing in Rapid Bedside Diagnosis of Spontaneous Bacterial Peritonitis: A Prospective Study

BACKGROUND AND AIMS

Spontaneous bacterial peritonitis (SBP) requires rapid diagnosis and the initiation of antibiotics. Diagnosis of SBP is usually based on cytobacteriological examination of ascitic fluid. These tests require good laboratory facilities and reporting time of few hours to 1-2 day. However, the 24 h laboratory facilities not widely available in country like India. We evaluated the diagnostic utility of reagent strip (Multistix 10 SG(®)) for rapid diagnosis of SBP.

MATERIAL AND METHODS

The study was prospectively carried out on patients of cirrhosis with ascites. Bedside leukocyte esterase reagent strip testing was performed on ascitic fluid. Cell count as determined by colorimetric scale of reagent strip was compared with counting chamber method. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated.

RESULT

Out of 100 patients with cirrhotic ascites, [72 males: 28 female; mean age 44.34 (SD 13.03) years] 18 patients were diagnosed to have SBP by counting chamber method as compared to 14 patients detected to have SBP by reagent strip test ≥++ positive. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of reagent strip ≥++ positive were 77.77%, 95.12%, 77.77%, 95.12% and 92% respectively compared to counting chamber method.

CONCLUSION

Reagent strip to diagnose SBP is very specific but less sensitive as compared to counting chamber method. This can be performed rapidly, easily and efficiently even in remote area of developing countries. This bedside test could be a useful tool for the diagnosis of SBP in country like India.

Diagnosis of spontaneous bacterial peritonitis: An update on leucocyte esterase reagent strips

Ascites remain the commonest complication of decompensated cirrhosis. Spontaneous bacterial peritonitis (SBP) is defined as the infection of ascitic fluid (AF) in the absence of a contiguous source of infection and/or an intra-abdominal inflammatory focus. An AF polymorphonuclear (PMN) leucocyte count ≥ 250/mm³ -irrespective of the AF culture result- is universally accepted nowadays as the best surrogate marker for diagnosing SBP. Frequently the results of the manual or automated PMN count do not reach the hands of the responsible medical personnel in a timely manner. However, this is a crucial step in SBP management. Since 2000, 26 studies (most of them published as full papers) have checked the validity of using leukocyte esterase reagent strips (LERS) in SBP diagnosis. LERS appear to have low sensitivity for SBP, some LERS types more than others. On the other hand, though, LERS have consistently given a high negative predictive value (> 95% in the majority of the studies) and this supports the use of LERS as a preliminary screening tool for SBP diagnosis. Finally, an AF-tailored dipstick has been developed. Within the proper setting, it is set to become the mainstream process for handling AF samples.

A new highly sensitive point of care screen for spontaneous bacterial peritonitis using the leukocyte esterase method

BACKGROUND & AIMS

Urine reagent strips measuring leukocyte esterase activity have been studied to screen spontaneous bacterial peritonitis (SBP) but are insensitive. We calibrated a strip specifically for ascitic fluid to achieve high sensitivity in this diagnosis.

METHODS

Experiments were conducted on ascitic fluid from patients with cirrhosis. Samples with SBP were diluted with native acellular ascitic fluid to achieve PMN counts below, above, and close to the diagnostic threshold of 250 PMN/microl. A model of SBP was created by spiking negative ascitic fluid samples (<250 PMN/microl) with activated PMN from blood of patients with sepsis, and diluted to achieve a range of PMN. Aliquots were tested at 2, 3, 4, and 10 min with the Periscreen leukocyte esterase strip. PMN/microl was correlated to timings and color scales: white defined negative (PMN <250/microl); and shades of brown, purple, and pink defined positive. Ascitic fluid samples were obtained from 58 patients. Negative ascitic fluid was used from 32 to generate the model SBP.

RESULTS

One thousand three hundred and four experiments were performed with a median PMN count of 492/microl (0-7510). After exclusion of uninterpretable colorimetric results, 1089 experiments were analyzed [PMN of 444/microl (0-7510)]. The best result was obtained at 3 min (n=299), with Se: 100%, Sp: 57.9%; NPV: 100%, PPV: 76.5%. The test was not interpretable in bloody, chylous or bilious ascitic fluid, or concurrent imipenem treatment.

CONCLUSIONS

This new leukocyte esterase strip calibrated to an ascitic fluid PMN count 250/microl is a robust screening tool when the strip turns any hue of tan/brown at 3 min.

A comparison of diagnostic efficacies among different reagent strips and automated cell count in spontaneous bacterial peritonitis

BACKGROUND

Currently, decision to give antibiotics in spontaneous bacterial peritonitis (SBP) suspected patient depends mainly on the result of manual cell count, which requires significant waiting period. Recently, many reports on the efficacies of reagent strips and a few reports of automated cell count are available but there has been no direct comparison study.

AIMS

This prospective study was to assess the diagnostic efficacies of different reagent strips (Aution, Multistix, Combur) and automated cell count.

METHODS AND RESULTS

A total of 250 paracenteses were performed. There were 40 specimens obtained from patients with clinical suspicion for SBP, the rest were obtained from non SBP suspected patients. Thirty specimens from 250 samples (12%) were diagnosed as SBP by manual cell count. Automated system provided higher value for SBP diagnosis in all parameters (sensitivity, specificity, PPV, NPV, and accuracy; 87.5-99.1%) whereas the strip tests provided lower number in all parameters (80-98.6%). Multistix provided the lowest sensitivity (80%). The false negative rates by Aution, Multistix, Combur tests and automated cell count were 10%, 20%, 10% and 3.3%, respectively. By lowering the cut off for SBP diagnosis with the automated system to 200 cells/mm(3), there was no false negative.

CONCLUSIONS

Comparing to reagent strips, automated cell count is a better screening tool for SBP diagnosis because it provides higher validity scores and a lower false negative rate. However, the discrepancy of cell count reading may occur, we suggest using a lower cut off for SBP diagnosis by the automated system.

Ascitic fluid analysis for diagnosis and monitoring of spontaneous bacterial peritonitis

Polymorphonuclear (PMN) cell count in the ascitic fluid is essential for the diagnosis and management of spontaneous bacterial peritonitis (SBP). To date, PMN cell count is routinely performed by traditional manual counting. However, this method is time-consuming, costly, and not always timely available. Therefore, considerable efforts have been made in recent years to develop an alternative test for a more rapid diagnosis and monitoring of SBP. The use of urinary reagent strips was proposed to achieve an “instant” bedside diagnosis of SBP. A series of reports evaluated the urine strip test for SBP diagnosis and reported promising results. However, a recent large multicenter study revealed a surprising lack of diagnostic efficacy of the urine screening test for SBP diagnosis. Another method, more recently proposed as an alternative to the manual PMN count, is the measurement of lactoferrin in ascitic fluid, but the data available on the diagnostic value of this test are limited to a single study. However, both urinary reagent strips and ascitic lactoferrin tests are qualitative methods and need, therefore, to be further confirmed by standard cytology of the ascitic fluid. To date, the only quantitative method proposed as a valid alternative to manual PMN counting is automated blood cell counters, commonly used in all laboratories for blood cell counting. Data available in the literature on the diagnostic performance of this method are limited but very promising, and this tool seems to have the potential to replace the manual counting method.

Leucocyte esterase reagent strips for the diagnosis of spontaneous bacterial peritonitis: a systematic review

The reported incidence of spontaneous bacterial peritonitis (SBP) is 7-30% per annum in cirrhotic patients. Timely diagnosis and treatment is crucial to reduce mortality owing to this infection. Recently, leucocyte esterase reagent strips have been tested in the diagnosis of infection in the ascitic fluid. The objective was to evaluate the diagnostic value of leucocyte esterase reagent strips in SBP in cirrhotic patients with ascites, by systematically reviewing the evidence from prospective clinical studies. We performed a comprehensive literature search in Medline up to July 2007 for adult human prospective clinical studies. Two reviewers independently checked all identified studies for fulfillment of predefined inclusion criteria, extracted data and assessed methodological quality of included studies. We had decided a priori to pool the studies via meta-analysis, only if statistical heterogeneity was found to be nonsignificant (P>0.10). Seventeen studies were included. Statistical heterogeneity among studies was found to be highly significant (P<0.001) in all analyses, precluding pooling of data for meta-analysis. Compared with the manual polymorphonuclear count ('gold standard'), leucocyte esterase reagent strips were found to have sensitivity ranging from 45 to 100%, specificity ranging from 81 to 100%, positive predictive value ranging from 42 to 100% and negative predictive value ranging from 87 to 100%. Despite the wide variation in sensitivity and positive predictive value between studies, the consistently high negative predictive value of leucocyte esterase reagent strips in SBP diagnosis should gain it a place in the ascitic tap diagnostic algorithm.

Review article: the utility of reagent strips in the diagnosis of infected ascites in cirrhotic patients

BACKGROUND

Spontaneous bacterial peritonitis (SBP) can be diagnosed via leucocyte esterase reagent strips, although diagnostic performances vary.

AIM

To perform critical review of literature on the use of reagent strips in SBP.

METHODS

Nineteen studies were analysed (Medline search), comparing reagent strips in cirrhotic ascites vs. cytobacteriological methods. Diagnostic grades (G) were: GO = 0 leucocytes/mm3; G1 = 15; G2 = 70; G3 = 125; G4 = 500 for Multistix, GO = 0; G1 = 25; G2 = 75; G3 = 500 for Nephur, Combur, UriScan, and GO = 0; G1 = 25; G2 = 75; G3 = 250; G4 = 500 for Aution.

RESULTS

Medians per study were: 75 patients (range: 31-1041), 136 ascites (47-2123), 17 SBP (5-117). For Multistix (12 studies), the sensitivities fell within the ranges 64.7-100% (G > or = 1), 45.7-83% (G > or = 2) and 45.3-89% (G > or = 3). For Nephur (n = 2), Combur (n = 6), UriScan (n = 1), sensitivities ranged 80.4-100% (G > or = 1), 63-100% (G > or = 2) and 67.7-97% (G > or = 3). For Aution (n = 3), sensitivities ranged 93-96% (G > or = 2) and 89% (G > or = 3). Nephur, Combur, UriScan displayed higher sensitivities than Multistix. However, in larger studies, sensitivities dramatically fell at 45.3% for Multistix (G > or = 3) if ascites polymorphonuclear count <1000/mm3 and 22.2% for bacterascites or 16.7-25% for asymptomatic patients.

CONCLUSION

Use of reagent strips for the diagnosis of SBP cannot be recommended, in view of low sensitivity and a high risk of false negatives, especially in patients with SBP and low polymorphonuclear count.

Evaluation of leukocyte esterase and nitrite strip tests to detect spontaneous bacterial peritonitis in cirrhotic patients

AIM

To investigate the diagnostic efficacy of leukocyte esterase and nitrite reagent strips for bedside diagnosis of spontaneous bacterial peritonitis (SBP).

METHODS

A total of 63 consecutive patients with cirrhotic ascites (38 male, 25 female) tested between April 2005 and July 2006 were included in the study. Bedside reagent strip testing was performed on ascitic fluid and the results compared to manual cell counting and ascitic fluid culture. SBP was defined as having a polymorphonuclear ascites count of >or= 250/mm(3).

RESULTS

Fifteen samples showed SBP. The sensitivity, specificity, positive and negative predictive values of the leukocyte esterase reagent strips were; 93%, 100%, 100%, and 98%, respectively. The sensitivity, specificity, positive and negative predictive value of the nitrite reagent strips were 13%, 93%, 40%, and 77%, respectively. The combination of leukocyte esterase and nitrite reagents strips did not yield statistically significant effects on diagnostic accuracy.

CONCLUSION

Leukocyte esterase reagent strips may provide a rapid, bedside diagnostic test for SBP.

Evaluation of leukocyte esterase and nitrite strip tests to detect spontaneous bacterial peritonitis in cirrhotic patients

AIM

To investigate the diagnostic efficacy of leukocyte esterase and nitrite reagent strips for bedside diagnosis of spontaneous bacterial peritonitis (SBP).

METHODS

A total of 63 consecutive patients with cirrhotic ascites (38 male, 25 female) tested between April 2005 and July 2006 were included in the study. Bedside reagent strip testing was performed on ascitic fluid and the results compared to manual cell counting and ascitic fluid culture. SBP was defined as having a polymorphonuclear ascites count of >or= 250/mm(3).

RESULTS

Fifteen samples showed SBP. The sensitivity, specificity, positive and negative predictive values of the leukocyte esterase reagent strips were; 93%, 100%, 100%, and 98%, respectively. The sensitivity, specificity, positive and negative predictive value of the nitrite reagent strips were 13%, 93%, 40%, and 77%, respectively. The combination of leukocyte esterase and nitrite reagents strips did not yield statistically significant effects on diagnostic accuracy.

CONCLUSION

Leukocyte esterase reagent strips may provide a rapid, bedside diagnostic test for SBP.

What's new in the treatment of ascites and spontaneous bacterial peritonitis

In recent years, there have been important advances in the clinical management of ascites and its related complications, such as hyponatremia, hepatorenal syndrome (HRS), and spontaneous bacterial peritonitis (SBP). Moreover, new drugs are currently being investigated for their potential usefulness in managing these complications. This article is not intended to comprehensively review all the literature published in recent years; rather, the authors discuss only studies they believe represent a potentially significant advance in this field. The following review is divided into two parts; the first discusses ascites and renal function abnormalities, including hyponatremia and HRS, and the second discusses SBP management.