Diagnosing ACS in Chest Pain With Normal ECG and Troponin
Despite substantial medical technology advances and the availability of troponin assay, the diagnosis of ACS remains challenging in the ED setting. This issue is even more problematic in patients with chest pain associated with non-diagnostic ECG and normal troponin in whom the diagnostic uncertainty is the greatest. Our study has the objective to validate in this category of patients, a new ACSD model combining a score describing chest pain characteristics and the TIMI score. We showed that our score (the ACSD score) had a good discriminative value with an excellent calibration. Diagnostic performance, as assessed by the area under the ROC curve of the ACSD score was significantly higher compared with Geleijnse score and TIMI score considered alone. The best threshold value of the ACSD score is 9 providing a good sensitivity (92%) and an excellent negative predictive value (99%), which is rated as good for the emergency rule-out for ACS.
ECG and cardiac troponin currently form the diagnostic cornerstones of clinical assessment of patients with chest pain. Unfortunately, ECG has a low sensitivity and normal biochemical markers are not infrequent. Surprisingly, there are only a few published decision rules to help clinicians to differentiate ACS from benign causes of chest pain. Most of the available models have either not been validated or have demonstrated mixed results. Moreover, no specific score exists to detect ACS in the selected group of patients with normal ECG and troponin. Yet, the rate of true ACS in this category of patients is significant suggesting the need for new instruments with higher sensitivity for prompt triage of patients with acute chest pain. In a recent study comparing several risk scores in patients with non-diagnostic ECG and normal troponin, 8% had positive exercise ECG, and almost two-thirds of these had coronary stenoses 50% or greater at angiography.
The Geleijnse score is based on detailed characteristic variables of chest pain without considering the patient's underlying health status which limits its usefulness as a diagnostic tool for ACS. This could explain its low performance for predicting ACS in our study. The improvement of the Geleijnse score when added to the TIMI score suggests the importance of combining items related to pain characteristics and underlying cardiovascular risk factors in the diagnostic process of ACS. Others scores such as HEART, GRACE and Banach scores were previously proposed mainly for prognostic information. Many patients presenting with possible ischaemic chest pain syndromes are hospitalised for observation and diagnostic testing. This triage could be substantially reduced by applying the ACSD score with regard to its excellent negative predictive value and its good sensitivity. In addition, all the variables of our score are readily available, an important condition for large clinical use. The fact that we included the TIMI score in the ACSD score is attractive in regard to this issue because the TIMI risk score is one of the most widely used risk models in patients with ACS. New technologies such as the 64-slice or greater cardiac multidetector tomography will probably become the near future diagnostic tool in ED patients with chest pain. However, in most low-income countries this category of medical facilities is unlikely to be available sooner.
Discussion
Despite substantial medical technology advances and the availability of troponin assay, the diagnosis of ACS remains challenging in the ED setting. This issue is even more problematic in patients with chest pain associated with non-diagnostic ECG and normal troponin in whom the diagnostic uncertainty is the greatest. Our study has the objective to validate in this category of patients, a new ACSD model combining a score describing chest pain characteristics and the TIMI score. We showed that our score (the ACSD score) had a good discriminative value with an excellent calibration. Diagnostic performance, as assessed by the area under the ROC curve of the ACSD score was significantly higher compared with Geleijnse score and TIMI score considered alone. The best threshold value of the ACSD score is 9 providing a good sensitivity (92%) and an excellent negative predictive value (99%), which is rated as good for the emergency rule-out for ACS.
ECG and cardiac troponin currently form the diagnostic cornerstones of clinical assessment of patients with chest pain. Unfortunately, ECG has a low sensitivity and normal biochemical markers are not infrequent. Surprisingly, there are only a few published decision rules to help clinicians to differentiate ACS from benign causes of chest pain. Most of the available models have either not been validated or have demonstrated mixed results. Moreover, no specific score exists to detect ACS in the selected group of patients with normal ECG and troponin. Yet, the rate of true ACS in this category of patients is significant suggesting the need for new instruments with higher sensitivity for prompt triage of patients with acute chest pain. In a recent study comparing several risk scores in patients with non-diagnostic ECG and normal troponin, 8% had positive exercise ECG, and almost two-thirds of these had coronary stenoses 50% or greater at angiography.
The Geleijnse score is based on detailed characteristic variables of chest pain without considering the patient's underlying health status which limits its usefulness as a diagnostic tool for ACS. This could explain its low performance for predicting ACS in our study. The improvement of the Geleijnse score when added to the TIMI score suggests the importance of combining items related to pain characteristics and underlying cardiovascular risk factors in the diagnostic process of ACS. Others scores such as HEART, GRACE and Banach scores were previously proposed mainly for prognostic information. Many patients presenting with possible ischaemic chest pain syndromes are hospitalised for observation and diagnostic testing. This triage could be substantially reduced by applying the ACSD score with regard to its excellent negative predictive value and its good sensitivity. In addition, all the variables of our score are readily available, an important condition for large clinical use. The fact that we included the TIMI score in the ACSD score is attractive in regard to this issue because the TIMI risk score is one of the most widely used risk models in patients with ACS. New technologies such as the 64-slice or greater cardiac multidetector tomography will probably become the near future diagnostic tool in ED patients with chest pain. However, in most low-income countries this category of medical facilities is unlikely to be available sooner.
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