Pros and Cons of VQ Scan vs. CT Angiography

Comparison of CT Pulmonary Angiography and V/Q Lung Scanning

While CT pulmonary angiography and ventilation-perfusion lung scanning (V/Q) are both crucial in the detection of pulmonary embolism, the two radiographic modalities have comparative advantages and limitations, which distinguishes their applicability. One clinical advantage that CT angiography has over V/Q is its sensitivity, which allows the test to detect emboli accurately. It reduces the likelihood of false positives by 89.4%, compared to 84.8% in V/Q. (Cadet, 2009). The advantage makes it more speedy and convenient in reducing the risk of adverse outcomes, as a blood clot in the pulmonary vein does not only increase the likelihood of unprecedented complications but also death. Timeliness is critical in preventing spillover effects.

Advantages of CT Scan

Another advantage is the fact that CT scan is more cost-consciousness, where it can be used in all cases. The clinical application is vital, considering the distribution of health resources is based on trade-offs. Instruments that can be utilized on a broad scale are always deemed more significant, as it is not to purchase all equipment. On their part, V/Q scans can only be used as a differential diagnosis of embolism among patients with normal x-rays. In the event of abnormal chest x-rays, a V/Q scan is harder to interpret and can be a source of misdiagnosis if used.

Advantages of V/Q Scan

Despite being less sensitive, V/Q scan is the best alternative among patients with compromised immune system as the case of HIV/AIDS patients, individuals with autoimmune diseases, as well as persons under chemotherapy. The edge over CT scan when dealing with the subset of the population arises from the fact that the nuclear test decreases exposure dose to radiation by 23% (Cadet, 2009). V/Q scans also preempt CT scans in the diagnosis of embolism among cases with renal insufficiency, as the iodinated contrast agents cannot be used because of associated adverse reactions (Fisher, 2007).

Factors Affecting BNP Test for Heart Failure Diagnosis

Disorders that Can Obscure the Diagnosis of Heart Failure Based on the BNP

Since its discovery, the B-type natriuretic peptide has emerged as a diagnostic test of immense clinical value. The biomarker is critical in not only the diagnosis of heart failure but also determining chances of mortality and long-term complications. Its relevance has attracted studies exploring the efficaciousness of the technique when used in diagnosing pulmonary embolism, myocardial infarction, and ischemia. Despite the extensive use, care must be taken when interpreting the results because confounding factors and comorbidities can compromise the specificity and sensitivity of the blood test. For instance, the method should not be used among patients with renal insufficiency. An underlying aspect is the fact that the health event is also associated with elevated levels of the endogenously produced human B-type natriuretic peptide. The pathophysiology raises concerns of negative predictive value and misdiagnosis in the event BNP test is employed, as the lusitropic properties can also be a presentation of the kidney disease. Colucci et al., (2000) confirm the observation by pointing out B-type natriuretic peptide is a signaling factor of disorders such as natriuresis and diuresis. The hormone is also a stimulatory element in endocrinal aspects such as the disruption of the renin–angiotensin–aldosterone axis that results in sodium retention and renal vasoconstriction.

The BNP tests should also be avoided among patients with metabolic disorders and flashy pulmonary edema. The caution should also be observed when dealing with the geriatric cases, as senescence have been found to increase NT-proBNP levels (Dodds, Kumar, & Veering, 2014). The elevations of the hormone in the blood, together with troponin levels, also indicate worsening prognosis of chronic pulmonary diseases. The clinical suspicion should thus not be used to confirm heart failure. Instead, BNP tests should be considered when making an adjunct decision about the treatment plan.


Cadet, J. (2009). V/Q scan less radiation risk than CT. Health Imaging. Retrieved 25 June 2017, from

Fisher, W. (2007). CT Versus V/Q Scan for Pulmonary Embolus. Retrieved 25 June 2017, from

Colucci, W. S., Elkayam, U., Horton, D. P., Abraham, W. T., Bourge, R. C., Johnson, A. D., & Haught, W. H. (2000). Intravenous nesiritide, a natriuretic peptide, in the treatment of decompensated congestive heart failure. New England Journal of Medicine, 343(4), 246-253.

Dodds, C., Kumar, C., & Veering, B. (Eds.). (2014). Oxford textbook of anaesthesia for the elderly patient. Oxford University Press.

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