Lactate and T (2) measurements of synovial aspirates at 1.5 T: differentiation of septic from non-septic arthritis

Assessment and diagnosis of the acute hot joint: a systematic review and meta-analysis

OBJECTIVES

Prompt diagnosis of septic arthritis (SA) in acute native hot joints is essential for avoiding unnecessary antibiotics and hospital admissions. We evaluated the utility of synovial fluid (SF) and serum tests in differentiating causes of acute hot joints.

METHODS

We performed a systematic literature review of diagnostic testing for acute hot joints. Articles were included if studying ≥1 serum or SF test(s) for an acute hot joint, compared with clinical assessment and SF microscopy and culture. English-language articles only were included, without date restriction. The following were recorded for each test, threshold and diagnosis: sensitivity, specificity, positive/negative predictive values and likelihood ratios. For directly comparable tests (i.e. identical fluid, test and threshold), bivariate random-effects meta-analysis was used to pool sensitivity, specificity, and areas under the curves.

RESULTS

A total of 8443 articles were identified, and 49 were ultimately included. Information on 28 distinct markers in SF and serum, differentiating septic from non-septic joints, was extracted. Most had been tested at multiple diagnostic thresholds, yielding a total of 27 serum markers and 156 SF markers. Due to heterogeneity of study design, outcomes and thresholds, meta-analysis was possible for only eight SF tests, all differentiating septic from non-septic joints. Of these, leucocyte esterase had the highest pooled sensitivity [0.94 (0.70, 0.99)] with good pooled specificity [0.74 (0.67, 0.81)].

CONCLUSION

Our review demonstrates many single tests, individually with diagnostic utility but suboptimal accuracy for exclusion of native joint infection. A combination of several tests with or without a stratification score is required for optimizing rapid assessment of the hot joint.

What are the best diagnostic tests for diagnosing bacterial arthritis of a native joint? : a systematic review of 27 studies

AIMS

This study aimed to answer two questions: what are the best diagnostic methods for diagnosing bacterial arthritis of a native joint?; and what are the most commonly used definitions for bacterial arthritis of a native joint?

METHODS

We performed a search of PubMed, Embase, and Cochrane libraries for relevant studies published between January 1980 and April 2020. Of 3,209 identified studies, we included 27 after full screening. Sensitivity, specificity, area under the curve, and Youden index of diagnostic tests were extracted from included studies. We grouped test characteristics per diagnostic modality. We extracted the definitions used to establish a definitive diagnosis of bacterial arthritis of a native joint per study.

RESULTS

Overall, 28 unique diagnostic tests for diagnosing bacterial arthritis of a native joint were identified. The following five tests were deemed most useful: serum ESR (sensitivity: 34% to 100%, specificity: 23% to 93%), serum CRP (sensitivity: 58% to 100%, specificity: 0% to 96%), serum procalcitonin (sensitivity: 0% to 100%, specificity: 68% to 100%), the proportion of synovial polymorphonuclear cells (sensitivity: 42% to 100%, specificity: 54% to 94%), and the gram stain of synovial fluid (sensitivity: 27% to 81%, specificity: 99% to 100%).

CONCLUSION

Diagnostic methods with relatively high sensitivities, such as serum CRP, ESR, and synovial polymorphonuclear cells, are useful for screening. Diagnostic methods with a relatively high specificity, such as serum procalcitonin and synovial fluid gram stain, are useful for establishing a diagnosis of bacterial arthritis. This review helps to interpret the value of various diagnostic tests for diagnosing bacterial arthritis of a native joint in clinical practice. Cite this article: Bone Joint J 2021;103-B(12):1745-1753.

Differences between infected and noninfected synovial fluid

AIMS

The diagnosis of joint infections is an inexact science using combinations of blood inflammatory markers and microscopy, culture, and sensitivity of synovial fluid (SF). There is potential for small molecule metabolites in infected SF to act as infection markers that could improve accuracy and speed of detection. The objective of this study was to use nuclear magnetic resonance (NMR) spectroscopy to identify small molecule differences between infected and noninfected human SF.

METHODS

In all, 16 SF samples (eight infected native and prosthetic joints plus eight noninfected joints requiring arthroplasty for end-stage osteoarthritis) were collected from patients. NMR spectroscopy was used to analyze the metabolites present in each sample. Principal component analysis and univariate statistical analysis were undertaken to investigate metabolic differences between the two groups.

RESULTS

A total of 16 metabolites were found in significantly different concentrations between the groups. Three were in higher relative concentrations (lipids, cholesterol, and N-acetylated molecules) and 13 in lower relative concentrations in the infected group (citrate, glycine, glycosaminoglycans, creatinine, histidine, lysine, formate, glucose, proline, valine, dimethylsulfone, mannose, and glutamine).

CONCLUSION

Metabolites found in significantly greater concentrations in the infected cohort are markers of inflammation and infection. They play a role in lipid metabolism and the inflammatory response. Those found in significantly reduced concentrations were involved in carbohydrate metabolism, nucleoside metabolism, the glutamate metabolic pathway, increased oxidative stress in the diseased state, and reduced articular cartilage breakdown. This is the first study to demonstrate differences in the metabolic profile of infected and noninfected human SF, using a noninfected matched cohort, and may represent putative biomarkers that form the basis of new diagnostic tests for infected SF. Cite this article: Bone Joint Res 2021;10(1):85-95.

Practical Considerations in Sepsis Resuscitation

BACKGROUND

Sepsis is a common condition managed in the emergency department, and the majority of patients respond to resuscitation measures, including antibiotics and i.v. fluids. However, a proportion of patients will fail to respond to standard treatment.

OBJECTIVE

This review elucidates practical considerations for management of sepsis in patients who fail to respond to standard treatment.

DISCUSSION

Early goal-directed therapy revolutionized sepsis management. However, there is a paucity of literature that provides a well-defined treatment algorithm for patients who fail to improve with therapy. Refractory shock can be defined as continued patient hemodynamic instability (mean arterial pressure, ≤ 65 mm Hg, lactate ≥ 4 mmol/L, altered mental status) after adequate fluid loading (at least 30 mL/kg i.v.), the use of two vasopressors (with one as norepinephrine), and provision of antibiotics. When a lack of improvement is evident in the early stages of resuscitation, systematically considering source control, appropriate volume resuscitation, adequate antimicrobial coverage, vasopressor selection, presence of metabolic pathology, and complications of resuscitation, such as abdominal compartment syndrome and respiratory failure, allow emergency physicians to address the entire clinical scenario.

CONCLUSIONS

The care of sepsis has experienced many changes in recent years. Care of the patient with sepsis who is not responding appropriately to initial resuscitation is troublesome for emergency physicians. This review provides practical considerations for resuscitation of the patient with septic shock. When a septic patient is refractory to standard therapy, systematically evaluating the patient and clinical course may lead to improved outcomes.

Evidence-based diagnostics: adult septic arthritis

BACKGROUND

Acutely swollen or painful joints are common complaints in the emergency department (ED). Septic arthritis in adults is a challenging diagnosis, but prompt differentiation of a bacterial etiology is crucial to minimize morbidity and mortality.

OBJECTIVES

The objective was to perform a systematic review describing the diagnostic characteristics of history, physical examination, and bedside laboratory tests for nongonococcal septic arthritis. A secondary objective was to quantify test and treatment thresholds using derived estimates of sensitivity and specificity, as well as best-evidence diagnostic and treatment risks and anticipated benefits from appropriate therapy.

METHODS

Two electronic search engines (PUBMED and EMBASE) were used in conjunction with a selected bibliography and scientific abstract hand search. Inclusion criteria included adult trials of patients presenting with monoarticular complaints if they reported sufficient detail to reconstruct partial or complete 2 × 2 contingency tables for experimental diagnostic test characteristics using an acceptable criterion standard. Evidence was rated by two investigators using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS). When more than one similarly designed trial existed for a diagnostic test, meta-analysis was conducted using a random effects model. Interval likelihood ratios (LRs) were computed when possible. To illustrate one method to quantify theoretical points in the probability of disease whereby clinicians might cease testing altogether and either withhold treatment (test threshold) or initiate definitive therapy in lieu of further diagnostics (treatment threshold), an interactive spreadsheet was designed and sample calculations were provided based on research estimates of diagnostic accuracy, diagnostic risk, and therapeutic risk/benefits.

RESULTS

The prevalence of nongonococcal septic arthritis in ED patients with a single acutely painful joint is approximately 27% (95% confidence interval [CI] = 17% to 38%). With the exception of joint surgery (positive likelihood ratio [+LR] = 6.9) or skin infection overlying a prosthetic joint (+LR = 15.0), history, physical examination, and serum tests do not significantly alter posttest probability. Serum inflammatory markers such as white blood cell (WBC) counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) are not useful acutely. The interval LR for synovial white blood cell (sWBC) counts of 0 × 10(9)-25 × 10(9)/L was 0.33; for 25 × 10(9)-50 × 10(9)/L, 1.06; for 50 × 10(9)-100 × 10(9)/L, 3.59; and exceeding 100 × 10(9)/L, infinity. Synovial lactate may be useful to rule in or rule out the diagnosis of septic arthritis with a +LR ranging from 2.4 to infinity, and negative likelihood ratio (-LR) ranging from 0 to 0.46. Rapid polymerase chain reaction (PCR) of synovial fluid may identify the causative organism within 3 hours. Based on 56% sensitivity and 90% specificity for sWBC counts of >50 × 10(9)/L in conjunction with best-evidence estimates for diagnosis-related risk and treatment-related risk/benefit, the arthrocentesis test threshold is 5%, with a treatment threshold of 39%.

CONCLUSIONS

Recent joint surgery or cellulitis overlying a prosthetic hip or knee were the only findings on history or physical examination that significantly alter the probability of nongonococcal septic arthritis. Extreme values of sWBC (>50 × 10(9)/L) can increase, but not decrease, the probability of septic arthritis. Future ED-based diagnostic trials are needed to evaluate the role of clinical gestalt and the efficacy of nontraditional synovial markers such as lactate.