It is a state in which the patient’s temperature is elevated, although examination fails to confirm the diagnosis, and even if a diagnosis is made, it is usually an exclusionary diagnosis, i.e., one that is reached by eliminating all possibilities until only one explanation remains.
Definition In 1961 Petersdorf and Beeson proposed the following criteria.
1. temperature repeatedly above 38.3 °C (101° F)? No diagnosis for at least 3 weeks? At least 1 week in the hospital for examination A new definition of FUO, in which outpatients (which reflects current medical practice) were given more weight, provided that
2, 3 outpatient follow-up visits or 3 days of treatment in the hospital without determining the cause, or 1 week of “smart invasive” outpatient testing without success.
Currently FUO cases are divided into four categories
Traditional FUO refers to the classification first proposed by Petersdorf and Beeson.
2. Hospital-onset FUO is defined as fever in patients admitted to the hospital for treatment for at least 24 hours. It is usually associated with hospital-related factors such as surgery, use of catheters, intravascular devices (i.e., “drips”, pulmonary artery catheters), medications (antibiotic-induced Clostridium difficile colitis, drug fever), and immobilization (bedsores). Sinusitis associated with nasogastric and transoral-tracheal tubes in the intensive care unit should also be considered, as well as lower extremity deep vein thrombophlebitis, pulmonary embolism, transfusion reactions, non-lithiatic cholecystitis, thyroiditis, alcohol/drug withdrawal, adrenal insufficiency, pancreatitis.
3. Immunodeficiency of immunodeficiency is present in patients receiving chemotherapy, or in patients with hematologic malignancies.
Fever is often accompanied by neutropenia (neutrophils < 500/uL) or impaired cell-mediated immunity.
The absence of an immune response masks a potentially dangerous process. Infection is the most common cause.
HIV-infected patients are a subgroup of immunodeficient FUO and often have fever. In the initial stages, it has an infectious mononucleosis-like disease with febrile manifestations. In the late stage of the infection fever is mostly the result of superimposed infection.
4. Some important causes extrapulmonary tuberculosis is the most common cause of unexplained fever.
Pharmacogenic hyperthermia, as the only symptom of adverse drug reactions, should be taken into account.FUO is also associated with pulmonary tuberculosis, histoplasmosis, coccidioidomycosis, bacillary, nodular disease and other disseminated granulomatous diseases . In adults, lymphoma is the most common cause of FUO. Thromboembolic disease (i.e. pulmonary embolism, deep vein thrombosis) , and occasionally fever. Although uncommon, the potential lethality of these diseases cannot be ignored. Infective endocarditis, although rare, is another important etiology to consider. Artificial fever is an underestimated cause. Patients are often women who work or have worked in the medical field and have complex medical histories.
A thorough diagnostic history (i.e., family members’ illnesses, recent tropical visits, medications), repeat physical examinations (i.e., rash, scabs, enlarged lymph nodes, heart murmurs), and an enormous number of laboratory tests (serum, blood cultures, immunology) are essential to find the cause.
Other tests are also necessary. Ultrasonography can show gallbladder stones, echocardiography, to diagnose infective endocarditis, and CT scan can show infections or malignancies in internal organs. Another technique is nuclear medical gallium 67 scan, which seems to be more effective in visualizing chronic infections. Definitive diagnosis may also require invasive techniques (biopsy and open surgery for pathology and bacteriology).
The use of radiolabeled fluorodeoxyglucose (FDG) positron emission tomography to target the source of unexplained fever has been reported to have a sensitivity of 84% and a specificity of 86%.
Despite all this, the diagnosis is also often suggested by the outcome of treatment. When a patient recovers after stopping medication, that may be drug fever, and when antibiotics or antifungals take effect, that may be infection. When other screening techniques fail to confirm the diagnosis, empirical treatment may be attempted.
Treatment
Unless the patient is acutely ill, treatment should not be given until the diagnosis is confirmed. This is because non-targeted treatment is rarely effective and most often delays the diagnosis. One exception is neutropenic patients, where delayed treatment may lead to serious complications. Immediately after blood culture collection, treat aggressively with powerful broad-spectrum antibiotics and later adjust antibiotics according to the blood culture results.
In HIV-infected patients with fever and hypoxia, medication for possible Pneumocystis carinii infection will be initiated. Once the diagnosis is made, treatment follows immediately.
Prognosis
Because of the wide range of conditions associated with FUO, the prognosis depends on the specific etiology. If no diagnosis is made after 6 to 12 months, the diagnosis will become increasingly difficult to establish. However, in this case, the prognosis is good.