Tag Archives: diagnosis

MRA for PE not very good

Wouldn’t it be great to have a reliable, radiation-free way to diagnose pulmonary embolism? Unfortunately, Magnetic Resonance Angiography is not it. In a study of 371 patients across 7 hospitals from the PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) investigators, the test was technically inadequate because of poor-quality images in 25% of cases. In those tests that were readable, the sensitivity was only 78%.

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: A Multicenter Prospective Study (PIOPED III)
Ann Intern Med. 2010 Apr 6;152(7):434-43

B lines be gone!

Vicki Noble’s Emergency Ultrasound team describe the resolution of Songraphic B lines on the lung ultrasound of a patient with end stage renal disease who presented with dyspnoea due to pumonary oedema which was treated with CPAP.
B-lines are hyperechoic vertical lines that originate at and slide with the pleura and extend radially to the edge of the screen without fading. Isolated B-lines may be seen in normal lungs, but diffuse B-lines in multiple zones indicate interstitial thickening, most commonly seen in congestive heart failure (CHF).

Image from cardiovascularultrasound.com

This case is interesting because it describes real-time resolution of B-lines during therapy in the ED demonstrating that in CHF, B-lines reflect acute rather than chronic changes within lung parenchyma.
Real-time resolution of sonographic B-lines in a patient with pulmonary edema on continuous positive airway pressure
Am J Emerg Med. 2010 May;28(4):541.e5-8

Bloodtest Not Pertinent (BNP)

Despite a lack of evidence that it’s useful, many emergency departments have introduced BNP testing. Some smart Australians decided to properly evaluate its benefit the best way possible – with a randomised controlled trial on 612 patients with acute severe dyspnoea. Guess what? Clinician knowledge of BNP values in patients who presented with shortness of breath to the emergency department did not reduce the probability of hospital admission or alter management or length of hospital stay. The study findings do not support indiscriminate BNP testing in all dyspnoea patients, but do not rule out a possible role in patients with milder dyspnoea.

B-type natriuretic peptide testing, clinical outcomes, and health services use in emergency department patients with dyspnea: a randomized trial
Ann Intern Med. 2009 Mar 17;150(6):365-71

Higher D Dimer cut-off in older patients

D-dimer levels below the conventional cut-off point of 500 µg/l combined with a “low/intermediate” or “unlikely” clinical probability can safely rule out the diagnosis in about 30% of patients with suspected pulmonary embolism.

However, the D-dimer concentration increases with age and its specificity for embolism decreases, which makes the test less useful to exclude pulmonary embolism in older patients; the test is able to rule out pulmonary embolism in 60% of patients aged <40 years, but in only 5% of patients aged >80.

A new, age dependent cut-off value was derived and then validated in two independent retrospective datasets from Belgium, France, the Netherlands, and Switzerland. They studied over 5000 patients aged >50 years.

The new D-dimer cut-off value was defined as (patient’s age x 10) µg/l in patients aged >50.

In 1331 patients in the derivation set with an “unlikely” score from clinical probability assessment, pulmonary embolism could be excluded in 42% with the new cut-off value versus 36% with the old cut-off value (<500 µg/l). In the two validation sets, the increase in the proportion of patients with a D-dimer below the new cut-off value compared with the old value was 5% and 6%. This absolute increase was largest among patients aged >70 years, ranging from 13% to 16% in the three datasets. The failure rates (all ages) were 0.2% (95% CI 0% to 1.0%) in the derivation set and 0.6% (0.3% to 1.3%) and 0.3% (0.1% to 1.1%) in the two validation sets.

Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism in older patients: a retrospective analysis of three large cohorts.

BMJ. 2010 Mar 30;340:c1475

Normal ECG still doesn’t rule out PE

ECGs from a prospective study of patients in the ED with suspected pulmonary embolism were studied to identify the relative frequency of ECG features of pulmonary hypertension. For a patient to be eligible for enrollment, a physician was required to have sufficient suspicion for pulmonary embolism to order objective diagnostic testing in the ED. Such testing included D-dimer measurement, computed tomography pulmonary angiography, ventilation/perfusion scanning, or venous ultrasonography.

ECGs were done in 6049 patients, 354 (5.9%) of whom were diagnosed with pulmonary embolism. The frequency, positive likelihood ratio (LR+) and 95% confidence interval (CI) of each predictor were as follows:

  • S1Q3T3 8.5% with pulmonary embolism versus 3.3% without pulmonary embolism (LR+ 3.7; 95% CI 2.5 to 5.4)
  • nonsinus rhythm, 23.5% versus 16.6% (LR+ 1.4; 95% CI 1.2 to 1.7)
  • inverted T waves in V1 to V2, 14.4% versus 8.1% (LR+ 1.8; 95% CI 1.3 to 2.3)
  • inversion in V1 to V3, 10.5% versus 4.0% (LR+ 2.6; 95% CI 1.9 to 3.6)
  • inversion in V1 to V4, 7.3% versus 2.0% (LR+ 3.7; 95% CI 2.4 to 5.5)
  • incomplete right bundle branch block, 4.8% versus 2.8% (LR+ 1.7; 95% CI 1.0 to 2.7)
  • tachycardia (pulse rate>100 beats/min), 28.8% versus 15.7% (LR+ 1.8; 95% CI 1.5 to 2.2).

The authors point out that the study may be subject to reporting bias or incorporation bias because those patients with ECG abnormalities may have then been more likely to undergo further evaluation for PE.

Overall, they summarise that the main findings were that the S1Q3T3 pattern and precordial T-wave inversions had the highest LR(+) values with lower-limit 95% CIs above unity, whether or not the patient had preexisting cardiopulmonary disease, but emphasise that the sensitivities of each of these findings were low, and clinicians should not decrease their suspicion for pulmonary embolism according to their absence.

Likelihood ratios and specificities were similar when patients with previous cardiopulmonary disease were excluded from analysis.
12-Lead ECG Findings of Pulmonary Hypertension Occur More Frequently in Emergency Department Patients With Pulmonary Embolism Than in Patients Without Pulmonary Embolism
Ann Emerg Med. 2010 Apr;55(4):331-5

Atypical chest pain renders AMI more likely

A prospective study of 796 ED patients with suspected cardiac chest pain assessed the value of individual historical and examination findings for diagnosing acute myocardial infarction (AMI) and the occurrence of adverse events (death, AMI or urgent revascularization) within 6 months. AMI was diagnosed in 148 (18.6%) of the 796 patients recruited.

The results may surprise some physicians:

Sweating observed by the ED physician was the strongest predictor of AMI (adjusted OR 5.18, 95% CI 3.02–8.86).

Reported vomiting was also a fairly strong predictor of AMI (adjusted OR 3.50, 1.81–6.77).

Pain located in the left anterior chest was found to be the strongest negative predictor of AMI (adjusted OR 0.25, 0.14–0.46).

Patients who described the pain as being the same as previous myocardial ischaemia were significantly less likely to be having AMI!

Following adjustment for age, sex and ECG changes, the following characteristics made AMI more likely (adjusted odds ratio, 95% confidence intervals):

  • pain radiating to the right arm (2.23, 1.24-4.00)
  • pain radiating to both arms (2.69, 1.36-5.36)
  • vomiting reported (3.50, 1.81-6.77), central chest pain (3.29, 1.94-5.61)
  • sweating observed by physician (5.18, 3.02-8.86)

Pain in the left anterior chest made AMI significantly less likely (0.25, 0.14-0.46)
The presence of rest pain (0.67, 0.41-1.10) or pain radiating to the left arm (1.36, 0.89-2.09) did not significantly alter the probability of AMI.

Compare these results with the American Heart Association guidelines which state that “chest or left arm pain or discomfort as the chief symptom reproducing prior documented angina” is associated with a high likelihood of ACS, or the European Society of Cardiology guidelines which state that “the typical clinical presentation of NSTE-ACS is retrosternal pressure or heaviness radiating to the left arm, neck or jaw”, which the authors of this study point out are statements made based on expert opinion for which references are not given.

The authors summarise with a powerful message: ‘Several ‘atypical’ symptoms actually render AMI more likely, whereas many ‘typical’ symptoms that are often considered to identify high-risk populations have no diagnostic value.’

The value of symptoms and signs in the emergent diagnosis of acute coronary syndromes
Resuscitation. 2010 Mar;81(3):281-6

Extreme white cell counts

Febrile children aged three months to three years with a white cell count over 25000/mm3 and fever were compared with controls whose leucoytosis was less extreme (15000-24999). The ‘extreme’ group had serious bacterial infection (SBI) in 39% compared with 15.4% controls. Pneumonia was the commonest SBI.

The authors conclude that in febrile children aged 3–36 months, the presence of extreme leucocytosis is associated with a 39% risk of having SBIs. The increased risk for SBI is mainly due to a higher risk for pneumonia. I conclude that leucocytosis is like fever: the cause may be benign, but the higher the number the less likely that is, even though the majority still won’t have SBI.

Extreme leucocytosis and the risk of serious bacterial infections in febrile children
Arch Dis Child. 2010 Mar;95(3):209-12

Identifying sick kids is still difficult

A systematic review to identify clinical features that have value in confirming or excluding the possibility of serious infection in children presenting to ambulatory care settings resulted in the calculation of likelihood ratios. Clinical features with a positive likelihood ratio of more than 5.0 were deemed red flags (ie, warning signs for serious infection); features with a negative likelihood ratio of less than 0.2 were deemed rule-out signs.

The features identified in several studies as red flags were :

  • Cyanosis (+LR range 2.66-52.20)
  • Rapid breathing (+LR 1.26-9.78)
  • Poor peripheral perfusion (+LR 2.39-38.80)
  • Petechial rash (+LR 6.18-83.70)]

In one primary care study the following were identified as strong red flags:

  • Parental concern (+LR 14.40, 95% CI 9.30-22.10)
  • Clinician instinct (+LR 23.50, 95 % CI 16.80-32.70)

Temperature of 40 degrees C or more had value as a red flag in settings with a low prevalence of serious infection.

What about ruling out serious illness?
Unfortunately, no single clinical feature had rule-out value but some combinations can be used to exclude the possibility of serious infection-for example, pneumonia is very unlikely (-LR 0.07, 95% CI 0.01-0.46) if the child is not short of breath and there is no parental concern.

An accompanying editorial sums up the challenge of paediatric emergency medicine in a nutshell:

“What is clear is that in 2010 we do not know how to effectively recognise or rule out severe disease in ill children and what is more, we do not even have a cohesive national or even global research strategy to address this problem.”

Diagnostic value of clinical features at presentation to identify serious infection in children in developed countries: a systematic review.
Lancet. 2010 Mar 6;375(9717):834-45

pain radiation to right arm in ACS

How predictive is the history for acute coronary syndrome? Of 1576 patients entered into a multicentre evaluation of chest pain units, 132 (8.4%)  had ACS, as determined by positive troponin, CK-MB, or early treadmill test.

On multivariate analysis, only age, duration, sex and radiation of pain to the right arm were independently associated with ACS.

Likelihood ratios (95% CI) were:

  • radiation of pain to the right arm, 2.9 (95% CI 1.4 to 6.3)
  • male sex 1.2 (95% CI 1.0 to 1.3)
  • female sex 0.79 (95% CI 0.62 to 1.0).

The area under the receiver operator characteristic curve for age was 0.629 (95% CI 0.573 to 0.686) and for duration was 0.546 (95% CI 0.481 to 0.610).

The authors conclude that clinical features have very limited value for diagnosing ACS in patients with a normal or non- diagnostic ECG, and radiation of pain to the right arm increases the likelihood of ACS.

Clinical diagnosis of acute coronary syndrome in patients with chest pain and a normal or non-diagnostic electrocardiogram.
Emerg Med J. 2009 Dec;26(12):866-70