Elsevier

Joint Bone Spine

Volume 80, Issue 6, December 2013, Pages 604-607
Joint Bone Spine

Original article
Usefulness and limitations of rapid urine dipstick testing for joint-fluid analysis. Prospective single-center study of 98 specimens

https://doi.org/10.1016/j.jbspin.2013.04.001Get rights and content

Abstract

Objective

To evaluate the diagnostic performance of rapid urine reagent strip testing of joint fluid in separating mechanical from inflammatory disease.

Methods

In a prospective single-center 12-month study of joint fluid specimens, leukocyte esterase reagent strip testing (LERST) was compared to leukocyte counts used as the reference standard. Leukocyte counts greater than 2000/mm3 were taken to indicate inflammation. Reproducibility of LERST was evaluated by testing 73 specimens twice and computing Cohen's kappa coefficient.

Results

Ninety-eight joint fluid specimens (26 with mechanical and 72 with inflammatory characteristics) were evaluated. LERST had 79.2% sensitivity, 92.3% specificity, 96.6% positive predictive value, 61.5% negative predictive value, a positive likelihood ratio of 10.3, and a negative likelihood ratio of 0.23. The kappa coefficient was 0.70 (0.53–0.87). Two negative LERSTs a few minutes apart had 80% negative predictive value and a negative likelihood ratio of 0.08.

Conclusion

LERST of joint fluid is a rapid means of satisfactorily separating mechanical from inflammatory joint fluids.

Introduction

Joint fluid analysis is pivotal in the diagnostic workup for joint effusions and arthritis. A high leukocyte count indicates an inflammatory process. The most widely used cut-off is 2000/mm3, despite some uncertainty about this choice [1], [2].

Septic arthritis is defined as the presence of culturable bacteria in the joint fluid and metabolic arthritis as the presence of microcrystals visible by polarized light microscopy (sodium urate in gout and calcium pyrophosphate dihydrate in articular chondrocalcinosis). No specific joint-fluid criteria exist for diagnosing inflammatory joint disease.

Reagent strip testing of urine is a validated tool for the rapid diagnosis of urinary tract infections via the detection of leukocyte esterase activity and/or nitrites [3], [4]. Reagent strips have also been of some usefulness in analyzing other body fluids. Thus, the negative predictive value (NPV) was excellent for infection of ascitic fluid [5] and the positive predictive value (PPV) was high in bacterial meningitis [6].

Here, our objective was to evaluate the diagnostic performance of leukocyte esterase reagent strip testing (LERST) of joint fluid in separating inflammatory from mechanical disease.

Section snippets

Methods

We studied joint fluid specimens collected for diagnostic purposes from patients evaluated at a rheumatology department over a 12-month period. For LERST, the specimens were collected in dry tubes and tested within 1 hour after collection using Combur10 Test® UX strips (F. Hoffmann-La Roche AG, Basel, Switzerland). In addition to leukocyte esterase activity, these strips assess nine other physicochemical parameters: specific gravity, pH, nitrites, protein, glucose, ketone, urobilinogen,

Statistics

Sensitivity (Se), specificity (Sp), PPV, NPV, and the positive and negative likelihood ratios (LR+ and LR−) were determined using the cell count performed at the laboratory as the reference standard. Means were compared using the Kruskal-Wallis test and percentages using the chi-square test (or Fisher's exact test when sample size was less than 5). Cohen's kappa coefficient was computed to assess reproducibility. P values smaller than 0.05 were considered significant.

Results

During the study period, 98 joint fluid specimens were analyzed. The main source joints were the knee (76.5%), hip (7.1%), shoulder (6.1%), wrist (4.1%), and elbow (3.1%). Cell counts indicated mechanical disease in 26 cases and inflammatory disease in 72 cases (metabolic disease, n = 30; chronic inflammatory joint disease, n = 30; septic arthritis, n = 7; and undetermined, n = 5). Table 1 reports the mean cell counts and percentage of neutrophils in each diagnostic subgroup.

In the group of

Discussion

Our findings demonstrate that rapid reagent strip testing for leukocyte esterase activity is useful as a screening tool for identifying inflammatory joint fluids. Thus, a positive LERST had an excellent PPV of more than 95% and an LR+ greater than 10.

These results are consistent with those reported by Ravaud et al. [7], who performed what is to our knowledge the only published study evaluating LERST of joint fluid from native joints. Blood cell counts and strips were used to test 208 joint

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

References (14)

There are more references available in the full text version of this article.

Cited by (15)

  • Modular design of a hybrid hydrogel for protease-triggered enhancement of drug delivery to regulate TNF-α production by pro-inflammatory macrophages

    2020, Acta Biomaterialia
    Citation Excerpt :

    Nonetheless, this drug-loaded hydrogel platform lacks a generalizable design framework, thus limiting the possibility of replacing its components to exploit alternative biological triggers. Specifically, drug release from this platform relies on the cleavage of ester bonds on the TG-18 backbone primarily by esterases, which are upregulated in inflammatory arthritis [25–27] but might not be a critical biological cue in other inflammatory diseases. Non-enzymatic hydrolysis of these ester bonds in the low pH environment associated with inflammatory conditions [28–30] might also result in undesirable non-specific drug release.

  • Performance of a new rapid diagnostic test the lactate/glucose ratio of synovial fluid for the diagnosis of septic arthritis

    2020, Joint Bone Spine
    Citation Excerpt :

    In the diagnosis of septic arthritis, their use could also allow earlier diagnosis than standard culture [23–25]. To overcome the time constraint, rapid assessment techniques, namely the use of glucometers and urine strips directly on the synovial fluid, were evaluated [26–28]. The primary objective of this study was to evaluate the clinical relevance and diagnostic performance of lactate and glucose concentration measurement in acute arthritis synovial fluid.

  • Leukocyte Esterase Strip Test Can Predict Subsequent Failure Following Reimplantation in Patients With Periprosthetic Joint Infection

    2017, Journal of Arthroplasty
    Citation Excerpt :

    Currently available tests such as the serum and synovial markers for infection, histology, and other tests fall short of providing this much needed information. The LE strip test has demonstrated efficacy for diagnosis of PJI, with an overall sensitivity between 66% and 100% and a specificity of 86.7%-100% [11,19,20,26-29]. The application of the LE test for timing of reimplantation and determination of persistence of infection was not known, which formed the impetus for performing this study.

View all citing articles on Scopus
View full text