4. DISCUSSION
As a result of this study, we found that 31.2% (n=54) of the patients who underwent thoracic and abdominal CT scans due to acute fever of unknown focus were positive for the source of infection. There were significant differences in age, presence or absence of chronic disease, and PCT level between the patients with and without an infection source on CT. We determined that the most important risk factors affecting the presence of infection on CT were age ≥ 65 years, presence of comorbidity, and PCT positivity.
Acute fever may be due to the source of infection, as well as various other causes, including pulmonary embolism, intracranial hemorrhage, drugs, and malignancy.2 Every person experiences fever many times in their lives. Most causes of acute fever are related to viral infections but patients may sometimes unexpectedly face serious conditions, such as sepsis and septic shock.6 The detection of the fever focus quickly and accurately with CT scans is very important for the initiation of appropriate treatment and survival;4 therefore, the use of CT in ED has increased in recent years.7 However, CT has certain disadvantages, such as deterioration in kidney function due to contrast agent use, exposure to radiation, and additional costs.8 Therefore, CT imaging should be performed after careful benefit/risk assessment of the advantages and disadvantages of this method. In our study, a source of infection was detected in CT scans in patients with comorbidities, those aged ≥ 65 years, and those with PCT positivity. If clinical benefit is presumed to be high in these patients, thoracic and abdominal CT scans can be performed to detect the focus of fever.
Advances in CT technology have allowed this imaging modality to be used both as a diagnostic and triage method.9 However, this can raise concerns in terms of the appropriate use of resources. The reasons for using CT to detect the source of infection in acute febrile patients without clinical clues in ED are blood parameters, such as WBC, CRP, and PCT being significantly higher than normal.10,11 and the need to determine whether there is an occult focus of infection and decide on hospitalization or outpatient treatment.12 In a previous study, PCT was found to be useful in the diagnosis of infection and had a higher diagnostic value than CRP in patients admitted to ED due to fever.13 PCT appears to be an earlier and better marker than inflammatory response parameters, such as CRP and leukocyte count in sepsis and serious infections.14 From these data, it can be concluded that clinicians often consider CT scans for possible infectious disease due to increased inflammatory markers. In the current study, we found that positive PCT was an effective parameter in detecting possible sources of infection in CT.
Diseases seen in the geriatric population may show a different course compared to other age groups and have more dramatic results. In the elderly, one of the most common causes of hospitalization is infections. The main reasons for this are the weakening of cellular and humoral immunity with aging, deterioration of physiological functions, such as the cough reflex, and comorbidities creating predisposition to infectious diseases. It may not always be possible to identify infections without delay in the elderly since they mostly progress with atypical findings in this population.15 The presence of fever in the elderly is a more serious indicator of disease compared to the younger age group. Delayed diagnosis and treatment and more severe infections increase morbidity and mortality rates.16 The results of our study indicate that thoracic and abdominal CT scans should be used more aggressively in elderly patients with high fever without clinical clues.