Point-of-care test identifies bacterial and viral causes of acute respiratory infections

27th October 2022

A point-of-care test shows good sensitivity for identifying both bacterial and viral pathogens in patients with acute respiratory infections

A point-of-care test has been found to correctly distinguish between bacterial and viral infections based on the host’s immune response, among patients with acute respiratory infections according to the results of a diagnostic study by team of US researchers.

Respiratory symptoms are the motive for a third of emergency room visits by both adult and paediatric patients. Acute respiratory infections due to either acute bronchitis, sinusitis, pneumonia and the common cold often present with overlapping symptoms leading to over-prescribing of antibiotics. Although multiplex PCR systems are available for the identification of bacterial and viral pathogens, an alternative strategy is to use a point-of-care test based on the host’s immune response to myxovirus resistance protein A (MxA) and C-reactive protein (CRP) in a finger-stick whole blood sample. To test the value of this approach in helping clinicians to decide on whether or not to prescribed antibiotics, in the present study, the US team examined the ability of the FebriDx^® which is a rapid, point-of-care diagnostic test that is designed to aid in the differentiation of bacterial and viral acute respiratory infections. The test can provide a result within 10 minutes by identifying myxovirus resistance protein A, which is induced by type 1 interferon due to viral infections and CRP, a non-specific acute-phase protein produced in response to inflammation and infection. While CRP is not specific for bacterial infections, if only MxA levels are elevated (i.e., no change in CRP) this is indicative of a viral infection. Similarly, elevated CRP in the absence of MxA, indicates a bacterial infection.

The US team recruited patients from emergency departments and outpatient settings who presented with new-onset respiratory symptoms including rhinorrhoea, nasal congestion, sore, throat, hoarseness, cough or shortness of breath and a recent fever and an asymptomatic control group. The point-of-care test was administered to both groups of patients although the treating physicians were blind to the test results. The primary outcome was set as a bacterial or viral-associated systemic host response. In addition, patient samples were collected and analysed by multiplex PCR for either viral or bacterial identification and which served as independent assessment of the point-of-care test result.

Point-of-care test and bacterial or viral identification

A total of 520 symptomatic patients with a mean age of 35.3 (44.2% male) were included and 170 in the asymptomatic group.

Final diagnostic information was available for 496 individuals and of whom, 14.7% had a confirmed bacterial and 59.7% a viral infection with the remainder classed as negative. The point-of-care test correctly identified 93.1% of bacterial infections giving a sensitivity of 93.2% (95% CI 84.9 – 97%), a specificity of 88.4% (95% CI 85 – 91.1%) and a positive predictive value of 58.1%.

For viral infections, the point-of-care test had a sensitivity of 70.3% (95% CI 64.8 – 75.2%), a specificity of 88% (95% CI 82.8 – 91.8%) and a positive predictive value of 89.7%. Interestingly, none of the participants had a co-infection which was defined as both a bacterial and viral pathogen plus a host response based on the independent assessment.

The authors concluded that the rapid diagnostic point-of-care test could help inform clinicians when assessing for either bacterial or viral causes for acute respiratory infections.

Citation
Shapiro NI et al. Diagnostic Accuracy of a Bacterial and Viral Biomarker Point-of-Care Test in the Outpatient Setting JAMA Netw Open 2022

Review suggests POC ultrasound highly sensitive for paediatric testicular torsion diagnosis

24th May 2022

POC ultrasound is a valuable tool to help emergency department clinicians identify testicular torsion in the paediatric population

Point-of-care ultrasound (POC ultrasound) has a high sensitivity and specificity for the identification of testicular torsion in paediatric patients within an emergency care setting. This was the conclusion of a systematic review and meta-analysis of studies by Japanese researchers from Tokyo, Japan.

Testicular torsion is defined as the rotation of the longitudinal axis of the spermatic cord, resulting in the absence of testicular blood flow. The estimated annual incidence of the condition among those younger than 18 years is 3.8 per 100,000 with a mean age of 10.6 years at presentation. Common symptoms include acute scrotum pain, erythema and scrotal swelling.

It has been suggested that a scoring system based on testicular swelling, a hard testicle, an absent cremasteric reflex, nausea/vomiting and high riding testis, can potentially diagnose or rule out testicular torsion in 80% of cases.

POC ultrasound use within an emergency department in children with suspected acute appendicitis has been shown to be diagnostic. Moreover, although ultrasound has been found to be an effective imaging modality for diagnosing testicular torsion in adult patients with acute scrotal pain, the diagnostic accuracy of POC ultrasound for testicular torsion in children has not been fully assessed.

In the current study, the Japanese team undertook a meta-analysis of studies in children (under 19 years of age) who presented at an emergency department with symptoms suggestive of an acute scrotum.

The researchers included any studies which used POC ultrasound but excluded both case studies and case series with less than 10 patients. The primary outcome was an assessment of the diagnostic accuracy of POC ultrasound for paediatric testicular torsion based on sensitivity and specificity.

POC ultrasound and testicular torsion

A total of four studies including 784 patients were included in the analysis. The median age of children in the four studies ranged from 10 to 13 (although it was not reported in one study).

Among the 4 studies, testicular torsion was identified via POC ultrasound in 205 patients although 3 of these were found to be false positives.

The pooled sensitivity was 98.4% (95% CI 88.5 – 99.8%) and the specificity was 97.2% (95% CI 87.2 – 99.4%). The overall false positive rate was 2.8% (95% CI 0.6 – 12.8) and the positive predictive value (i.e., the probability that an individual has the condition) was 84.9%.

Based on their analysis, the researched felt that POC ultrasound had the potential to allow clinicians to diagnose testicular torsion rapidly and safely. They added that children with a positive result should undergo immediate exploratory surgery. However, an important caveat from their analysis was how the quality of the available evidence was only moderate because of a high risk of bias and heterogeneity.

The authors concluded that although POC ultrasound appeared to be able to accurately diagnose testicular torsion, prior to implementing such as recommendation, prospective studies were required to clarify the accuracy of this imaging modality.

Citation
Mori T et al. Diagnostic accuracy of point-of-care ultrasound for paediatric testicular torsion: a systematic review and meta-analysis Emerg Med J 2022

Hand-held and high-end vascular ultrasound devices show good agreement for carotid disease detection

25th February 2022

Hand-held carotid ultrasound has been demonstrated to have good agreement with conventional duplex ultrasound in ruling out carotid disease

A hand-held carotid ultrasound device shows an acceptable level of agreement with conventional duplex ultrasound for the examination of patients with suspected transitory ischaemic attack (TIA) or ischaemic stroke. This was the conclusion by a team of researchers from the Department of Internal Medicine, Levanger Hospital, Norway.

According to the World Stroke Organisation, 1 in 4 adults over the age of 25 will have a stroke in their lifetime and in 2019, there were 12·2 million incident cases of strokes, accounting for 11.6% of all global deaths.

Moreover, the presence of narrowing of the carotid artery or carotid stenosis, has been found to be associated with increased risk of ischaemic stroke. Carotid endarterectomy as a treatment, has been found to be of some benefit for patients with 50% to 69% symptomatic stenosis, in reducing the risk of stroke.

However, carotid stenosis cannot be adequately assessed through a physical examination and carotid ultrasonography has become a reproducible imaging method used to detect carotid atherosclerosis.

But could a hand-held carotid and hence much more portable, ultrasound device be just as reliable for the examination of patients with suspected TIA or an ischaemic stroke compared to a conventional high-end vascular ultrasound (HIGH)? This was the essential question addressed in the current study by the Norwegian team.

They included patients admitted to a community hospital with a suspected stroke or transient ischaemic attack. The patients were examined using a hand-held carotid ultrasound and the severity of carotid stenosis graded on a 7-point ordinal scale from 1 (normal) to 7 (occluded). Following this initial assessment, a HIGH was performed by a second cardiologist who remained unaware of the findings from the hand-held device and graded the degree of stenosis using the same scale.

The results of the two scans were then compared by weighted Cohen’s Kappa and which is designed to assess the level of agreement between the two techniques. Scores range from 0 to 1 with 0.41 – 0.60 rated as moderate agreement, 0.61 – 0.80 as substantial and over 0.81 as almost perfect agreement.

Hand-held carotid ultrasound agreement with HIGH

A total of 80 patients with a mean age of 71.5 years (47.5% women) were included in the study, 27.5% of whom, had a previous history of cardiovascular ischaemic events (i.e., ischaemic stroke, TIA, or myocardial infarction). From the total cohort, 11% were found to have a greater than 50% internal carotid stenosis (ICS) on examination. Overall, 77.5% of patients were discharged with a diagnosis of ischaemic stroke or TIA.

The overall agreement between the hand-held device and HIGH for the classification of the degree of internal carotid stenosis was 69%. In addition, the weighted Kappa agreement between the hand-held device and HIGH was 0.76 (95% CI 0.66 – 0.85). Nevertheless, there was evidence that the hand-held device overestimated ICS compared to HIGH when there was >50% occlusion (odds ratio for agreement = 0.15, 95% CI 0.06 – 0.42) using < 50% stenosis as the reference.

In discussing their results, the authors stated that there was a strong correlation between ICS grading between the hand-held carotid device and HIGH. They concluded that examining the level of carotid stenosis with a hand-held device was a reliable method for ruling out significant carotid artery disease.

But given the potential for overestimation when the carotid stenosis was greater than 50%, the authors suggested that the hand-device device should not be used for detailed classification of carotid disease.

Citation
Saxhaug LM et al. Reliability and agreement of point-of-care carotid artery examinations by experts using hand-held ultrasound devices in patients with ischaemic stroke or transitory ischaemic attack Open Heart 2022

Point-of-care COVID-19 test in ED significantly reduces turnaround-time

7th January 2022

Point-of-care COVID-19 testing in an emergency department has been found to be highly accurate and significantly reduces turnaround-time

The use of a point-of-care (POC) COVID-19 test within an emergency department (ED) has been found to significantly reduce the turn-around- time compared to PCR tests among patients in need of hospital treatment. This was the key finding of an analysis by a team from the Department of Emergency and Acute Medicine, Charite Universitatsmedizin, Berlin, Germany.

The COVID-19 pandemic has placed enormous strain on healthcare systems across the globe and this has been particularly true for emergency departments (EDs) since patients, even with mild symptoms tend to intuitively present at an ED when they believe they have a serious disease. An ED therefore requires access to a fast and accurate means of testing patients for COVID-19 when they present at the department.

The gold standard test for COVID-19 is a PCR test although results are not available for between 4 and 24 hours . The use of rapid antigen tests offers a potentially faster alternative but research has shown that while these tests are useful for symptomatic patients in the emergency setting, patients testing negative require confirmation by PCR test and should isolate until this result becomes available.

With a need for a rapid COVID-19 test result among all patients potentially requiring urgent inpatient care, for the present study, the German team set out to evaluate the role of a POC COVID-19 test for use in the ED. All inpatients were routinely screened at the researcher’s hospital for COVID-19 and they retrospectively examined the clinical characteristics and in-hospital follow-up data for all patients from the electronic medical records.

For the study, the team set the primary outcome measure as the turn-around-time (TAT) for the POC compared to the standard PCR test result as well as examining the diagnostic performance of the device which was integrated with the hospital LAN system and ordered via the laboratory channel and ED.

Findings

A population of 160 patients with a mean age of 68 years (69% female) were included and of whom, 16 tested positive for COVID-19 using the POC. The most common symptoms of COVID-19 were dyspnoea (37.5%), fever and cough (both 25%).

The POC had a sensitivity and specificity of 100% and the test result was available within a median of 102 minutes after admission compared to a median of 811 minutes for the PCR test (p < 0.001).

Among patients requiring an intervention within 6 hours of presentation (e.g., severe trauma, myocardial infarction), the POC test result was available before the intervention in 92.1% of patients compared to only 5.4% of those with a PCR test result.

The authors concluded that the device could be easily incorporated into an ED and that it showed a high diagnostic performance.

Citation

Mockel M et al. SARS-CoV-2 screening in patients in need of urgent inpatient treatment in the Emergency Department (ED) by digitally integrated point-of-care PCR: a clinical cohort study. MedRxiv 2022.