The modern concept of unexplained fever refers to the difficult patients with fever as the main clinical manifestation, which cannot be clearly diagnosed after more detailed medical history, physical examination and routine laboratory tests in outpatient and emergency departments, and is regarded as the “crown” in the field of internal medicine. Therefore, the diagnosis and treatment of unexplained fever requires doctors to establish the most reasonable mode of thinking in diagnosis and treatment, which is a concentrated form of knowledge and experience, and is the crystallization of long-term study and repeated practice.
Step 1: Determine the presence of fever
The diagnostic criteria for fever have been controversial. In many current studies, the time point and method of temperature monitoring are also not clearly mentioned. If some of the above factors are taken into account, some scholars believe that fever can be defined as: measurement of oral temperature, morning temperature > 37.2℃, and random temperature > 37 .8℃ at other times.
Commonly patients only subjectively feel an increase in body temperature, but in fact is not really fever, or the patient measured body temperature higher than 37 ℃ (98.6 ° F) is considered abnormal; body temperature can be affected by metabolic rate, physical activity outside temperature and body mass, and there are fluctuations within the range of 1.7 ℃ (3 ° F) day and night; therefore, the afternoon or evening oral temperature up to 37.7 ℃ (100 ° F) may be completely normal.
The body temperature of healthy people is relatively constant, and its measurement is more accurate with rectal temperature (36.9-37.9℃), which is often considered as the “best temperature scale”; it is more convenient to measure oral temperature, which is 0.3℃ lower than rectal temperature; axillary temperature is also more convenient, which is 0.4℃ lower than oral temperature; under normal circumstances, the body temperature is low in the morning and high in the evening, and the daily difference is not Under normal circumstances, body temperature is low in the early morning and high in the evening, and the daily difference is not more than 1℃, more than 1℃ can be diagnosed as fever. There are also individual differences in body temperature; most people have a temperature lower than 37℃; however, elderly people have a lower metabolic rate and a lower body temperature than young people; young children have an underdeveloped nervous system, poor regulation and fluctuate greatly; young women have a high temperature during pregnancy and premenstruation.
Step 2: Distinguish between long-term fever, short-term fever and unexplained fever
Fever is mainly of two types.
1. Acute fever that can generally subside on its own within 2-3 weeks, mainly some viral infections, whose diagnosis is often inferential and treatment is also empirical.
2. Long fever course, high fever, long duration of fever, and long-term misdiagnosis.
It can also be classified according to the level of fever and the duration of the disease into.
1.Acute fever: fever duration in 1-2 weeks.
2.Long-term fever: the duration of the disease is more than 2 weeks, and the body temperature is above 38.5℃.
3. Periodic fever: recurrent or regular fever.
4.Long-term hypothermia: chronic slight fever, body temperature of 37.4-38.4℃ for more than 4 weeks.
5.Ultra-high fever: body temperature over 41℃, sudden onset.
(1) Acute fever: Patients who do have acute fever usually have an obvious cause for the fever because they have symptoms, past medical history, physical examination and simple laboratory results for reference. Tests should include cultures from blood, other abnormal body fluids or skin lesions, complete blood counts, urinalysis, and chest radiographs. Liver function tests are not necessary for every patient, but they are useful. Many fevers are caused by viral infections, so it is helpful to know if there is an “epidemic” of viral infections; although the course of a few viral illnesses may be long, the majority of fevers last only a few days, except in the case of EBV and cytomegalovirus infections.
(2) Prolonged fever: Even if the patient observes a prolonged “fever”, if the fever is not accompanied by leukocytosis, anemia, or acute phase of the disease (sedimentation, fibrinogen, C-reactive protein), and if there are no symptoms indicating damage or abnormalities in a particular area of the body, then the likelihood of serious disease is The likelihood of having a serious disease is very low. Some patients often conclude prematurely that they are ill when they observe a prolonged “fever”, which must be repeatedly observed to confirm that they are wrong, and even requires psychotherapy to relieve their doubts. Even if the patient’s complaint of “fever” is indeed possible, careful history collection, careful patient observation and reasonable use of non-invasive laboratory tests should be performed in order to make an appropriate evaluation.
(3) Unexplained fever: The broad concept of unexplained fever refers to all patients with unexplained fever. However, the narrow concept of fever of unknown origin is also used in clinical practice.
The diagnosis is mainly based on Petersdorf’s criteria.
1, duration of fever ≥ 3 weeks.
2, repeated body temperatures ≥38.3°C.
3.After a week of detailed examination, the diagnosis is still not clear. The above three conditions must be met simultaneously to make the diagnosis.
The advantages of this concept are mainly as follows
1.Excluding certain viral infections that can be diagnosed definitively.
2.Excluding short-term fever whose etiology is clearer and easier to diagnose.
3.Excluding fever of unknown origin that can be spontaneously resolved in a short period of time.
4. functional fevers that manifest as low fever were excluded.
Therefore, the concept of fever of unknown origin (FUO) actually refers to that part of the disease group that is truly and more difficult to diagnose.
Step 3: Re-classify fever of unknown origin
Patients with fever of unknown origin are then classified into 4 subtypes – classic: nosocomial, immunodeficiency, and HIV-related – based on relatively clear underlying etiology.
The most common causes of classic FUO include infectious diseases, malignant neoplastic diseases, and connective tissue and inflammatory vascular diseases.
2. Nosocomial type: FUO with fever at least 24 hours after hospitalization and no obvious signs of infection before admission, and undiagnosed for at least 3 days can be considered for this diagnosis; such diseases include septic thrombophlebitis, pulmonary embolism, Clostridium difficile small intestinal colitis and drug fever; sinusitis may also be a cause in patients with nasogastric intubation or nasotracheal intubation.
3, Immunodeficiency type: is a recurrent fever in patients with a neutrophil count of 500/mm3 or less that remains undiagnosed after 3 days; the cause of fever in most patients in this category is an opportunistic bacterial infection; broad-spectrum antibiotics are usually used to cover the most likely causative agent; fungal infections caused by Candida albicans and Aspergillus must also be considered; rare are viral infections such as herpes zoster and cytomegalovirus.
4. HIV-associated type: includes recurrent fever lasting 4 weeks in HIV-infected outpatients or 3 days in hospitalized HIV-infected patients; although acute HIV infection is an important cause of classic FUO, HIV can predispose patients to opportunistic infections; such diseases include Mycobacterium avium infection, Pneumocystis carinii pneumonia, and cytomegalovirus infection. Non-infectious causes of FUO are rare in HIV-infected patients; such diseases include: lymphoma, Kaposi’s sarcoma and drug fever, and the patient’s geographic location is particularly important information when considering such diseases.
Step 4: Look for diagnostic clues to classic unexplained fever (longitudinal thinking)
In the clinical diagnosis of fever of unknown origin, it is necessary to consider things in terms of their personality. “One leaf falls to know the whole world”. Certain clinical manifestations, which can be the key to clear diagnosis and shorten the diagnosis time, namely, the longitudinal thinking diagnostic method, also called characteristic thinking diagnostic method, which has been proposed by the author, is a longitudinal thinking mode, whose main method is to seize an interesting characteristic point in clinical manifestations, physical examination and preliminary laboratory tests, cut directly into the etiology proper and start the related examination plan and treatment plan. The diagnostic method of characteristic thinking is the concrete embodiment of the principle of modeling clinical diagnostic thinking, which requires clinicians to establish the most reasonable diagnostic and therapeutic thinking model for the common causes of fever of unknown origin on the basis of continuous optimization of systematic thinking, which is a concentrated form of knowledge and experience, and is the crystallization of long-term learning and repeated practice. Therefore some clinical patients with fever of unknown origin have some diagnostic features, or syndromes, and clinicians should learn to be good at grasping these diagnostic features or clues. For example
1, a middle-aged male patient with fever unexplained for more than a month, accidental examination found “testicular tenderness”, according to this important clinical features, the follow-up of the epidemic area contact history, brucella antibody positive, the diagnosis of brucellosis; that is, “testicular pain of unexplained fever need to exclude brucellosis”. .
2.Middle-aged female with fever for more than one week, antipyretic and antipyretic drugs such as flumethasone were ineffective, and only chlorpromazine could reduce the fever; central system pathology was considered, and magnetic resonance showed pituitary stroke; i.e., “fever with ineffective general antipyretic drugs and glucocorticoids needs to be excluded from central fever, and often requires chlorpromazine to reduce fever.
3.An elderly woman with fever for more than half a year, and a number of examinations conducted at several large hospitals failed to find the cause of the fever.
4. A patient with unexplained fever presented with enlarged cervical lymph nodes, and ultrasonography showed that the cervical lymph nodes were fused with each other; lymph node fusion was the most important clinical feature of this patient. Previous experience has shown that the main diseases that can cause lymph node fusion in clinical practice are lymphoma, tuberculosis and nodal disease; the next diagnostic tests along these lines are performed to clarify the diagnosis.
Lymph node enlargement can be classified as.
(1) Infectious lymph node enlargement: fever accompanied by local or generalized lymph node enlargement with pressure pain is characteristic of bacterial or viral infection, tuberculous lymph node enlargement course is moderately hard, pressure pain, but there may be spontaneous pain, lymph nodes may be arranged in bunches or fused with each other, and may also adhere to the skin.
(2) Tumor lymph node enlargement: progressive, persistent enlargement, often without the tendency to shrink; lymph node enlargement caused by malignant tumors is clinically most common in metastatic cancer. Lymph node metastasis in the left supraclavicular fossa (Virchow’s lymph node) mostly originates from cancers of the gastrointestinal tract such as the stomach, while supraclavicular lymph nodes mostly originate from cancers of the esophagus, mediastinum and lung. Metastatic cancer lymph nodes are characterized by hard texture, irregular edges and surface; enlarged lymph nodes in malignant lymphoma and leukemia are mostly generalized, painless, tough, with rubber-like elasticity, smooth surface and asymmetry. The swollen lymph nodes of malignant lymphoma may adhere to each other to form a mass, and there may be painful lymph nodes or bone pain after drinking alcohol as one of their characteristics.
(3) Swollen lymph nodes in connective tissue disease: Generally, the swollen lymph nodes are more common in the axillae, followed by the neck, and the swollen lymph nodes are painless and soft, ranging from the size of a grain of rice to several centimeters, and are characterized by their growth and decline in relation to disease activity.
In addition, necrotizing lymphadenitis should be considered when the lymph nodes in the neck are swollen and painful after “upper sensation”; the main point of lymph node pathological examination is to pay attention to the integrity of the lymph nodes, and the pathological changes of necrotizing lymphadenitis are similar to those of tuberculosis infection.
5, abnormal lymphocytosis, normal blood can occasionally see heterotypic lymphocytes, also known as Downey cells, or viral cells, known to be T lymphocytes, according to their morphology can be divided into 3 types: type I: cytoplasm dark blue, appearing vacuole; type II: cell volume is larger, darker staining; type III: naive type, chromatin is fine, visible nucleoli. It is mostly below 1% in normal. In viral hepatitis, epidemic hemorrhagic fever, and post-transfusion syndrome (probably cytomegalovirus infection), the increase can be seen, and the cells are diagnostic for viruses when they are above 5%, and can exceed 10% or even 20-30% in infectious mononucleosis. Heterozygous lymphocytes can also be seen in malaria, tuberculosis, brucellosis and p-aminosalicylate, phenytoin sodium and other drug reactions.
6.Rash.
(1) Erythema annulare is a kind of circular skin damage spreading on the trunk and extremities, which is one of the criteria for diagnosing rheumatic fever.
(2) Wandering erythema is a clinical feature of Lyme disease.
(3) The rash damage of Epstein-Barr virus infection and mononucleosis caused by cytomegalovirus infection is generally mild, but if penicillin or ampicillin antibiotics are given for these two viral infectious diseases, significant maculopapular skin damage can occur in 50-90% of patients, and this condition does not imply an allergy to penicillin antibiotics, but is suggestive of the etiology This condition does not imply an allergy to penicillin antibiotics, but is suggestive of the etiology.
(4) The typical early manifestation of endemic typhus is the appearance of non-fading papules on the distal ends of the extremities (including the palms of the hands and soles of the feet); in the later stages of the disease, the papules spread to the trunk, and prolonged papules may develop into subcutaneous punctate hemorrhages.
(5) The rash of epidemic typhus is first seen in the axillae and then extends to the distal ends of the limbs, usually without invading the palms of the hands and soles of the feet.
(6) Drug rash does not necessarily have pruritus. If a rash appears after taking medication in a febrile person, drug fever and infectious diseases should be suspected; if fever and rash appear after using medication, drug fever is more likely.
7. Other.
(1) thrombocytopenia combined with renal damage or psychiatric symptoms, peripheral blood appears broken red blood cells, to consider thrombotic thrombocytopenia.
(2) Patients with long-standing pneumonia need to exclude obstructive pneumonia (lung tumor); unexplained hyponatremia should be considered ectopic endocrine syndrome due to tumor (especially lung cancer).
(3) Rapid disappearance of premenstrual fever at the onset should be considered genital tuberculosis.
(4) Patients with short-term fever combined with renal damage should be excluded from leptospirosis; systemic diseases combined with renal damage should be excluded from connective tissue disease.
(5) Patients with sepsis-like pulmonary edema should be considered for capillary leak syndrome.
(6) The cause of fever in tumor patients is often tumor deterioration (e.g., extensive metastasis of solid tumors, lymphoma involving internal organs, etc.) or infection, which is often caused by gram-negative bacilli or fungi and is often accompanied by neutropenia.
(7) Unexplained multisystemic damage or unexplained disease needs to be considered poisoning [9].
(8) Hidden lesions that can be easily overlooked: infections of the liver, subdiaphragm, spine, pelvis, paranasal sinuses and mastoid process; paraspinal abscesses after spinal lesions or sepsis; fundus examination is useful for detecting cornified tuberculosis, and anal finger examination is useful for detecting prostate and pelvic abscesses, so it should be included as a routine examination.
(9) The specific reaction of tuberculin test for the diagnosis of tuberculosis in adults, the diagnostic significance of a negative result excluding tuberculosis is greater than the general significance of a positive result affirming tuberculosis.
Step 5: Classical unexplained fever without diagnostic clues using probabilistic diagnosis method (lateral thinking)
Many patients with clinically unexplained fever do not have diagnostic features. When encountering these patients, clinicians are often confused and do not know where to start with the examination and treatment. At this time, the probabilistic thinking method should be used to find out the diagnostic direction from a macroscopic perspective and arrange further diagnostic and treatment plans. The so-called probabilistic method is a lateral mode of thinking, that is, from the general clinical data, according to the probability of the onset of different diseases, to find out the general diagnostic direction, including
1.Infectious diseases.
2.Malignant tumors.
3, connective tissue diseases.
4, other disease categories.
5, undiagnosed.
In total, there are 5 major categories, and the most clinically significant are the first three categories of diseases. List the priority and differential diagnosis needed for several categories of diseases, and then start the corresponding examination plan. For example, a young woman with unexplained fever for 5 years, connective tissue disease is considered first. This is because in terms of probability of onset.
(1) As the duration of fever increases, infectious diseases gradually decrease and tumors and connective tissue diseases increase.
(2) The longer the time and the younger the age, the greater the proportion of connective tissue disease.
Therefore, the diagnostic direction for this patient was connective tissue disease.
In an elderly patient with fever for more than 2 months, then the first diseases considered from the point of view of probability of onset are: atopic infectious diseases such as tuberculosis, hematologic tumors, and vascular inflammatory connective tissue diseases. This is because: infectious diseases gradually decrease and tumors and connective tissue diseases increase with the prolongation of fever; the longer the duration and the older the patient, the greater the proportion of tumor diseases; giant cell arteritis takes the first place among connective tissue diseases in the elderly; among FUO in the elderly, the proportion of solid tumors decreases and hematologic system tumors increase with the prolongation of fever. Therefore, the probabilistic thinking method was used to determine the above three diagnostic directions and arrange the corresponding examinations. If, during the examination, characteristic information is found, for example, blood tests reveal an increase in rheumatism-related antibodies, then the characteristic thinking method is shifted from the original horizontal thinking to vertical thinking, and the examination and treatment are centered around rheumatic diseases, especially vasculitic diseases.
Main laws.
1.The overall distribution law
(1) Infectious diseases account for about 38.0% of the total number of FUO and are its most common cause; followed by connective tissue and inflammatory vascular diseases, accounting for about 1/3 of the total number of FUO; neoplastic diseases are 11.7%; other diseases are 9.3%; and other undiagnosed diseases are about 7.8%.
(2) Infectious diseases and connective tissue and inflammatory vascular diseases, which together accounted for more than 2/3 of FUO (71.2%); (3) tuberculosis infection accounted for about half of infectious diseases (51.9%).
(4) Connective tissue and inflammatory vascular diseases accounted for the highest proportion of adult Still’s disease, accounting for about 51.5% of connective tissue and inflammatory vascular diseases.
(5) Among the neoplastic diseases, lymphoma accounted for the highest proportion (56.9%).
(6) Among other diseases, drug fever and necrotizing lymphadenitis were the main ones.
(7) The rates of infectious diseases, connective tissue diseases and other diseases increased in the past 10 years compared with the previous 10 years, while the rates of neoplastic diseases and undiagnosed diseases decreased compared with the previous 10 years.
2.Related patterns of factors
(1) The relationship between fever duration and etiology. As the duration of fever increases, the number of infectious diseases gradually decreases, while the number of neoplastic diseases and connective tissue diseases increases. The average fever duration was 81.3 days for infectious diseases, 132.5 days for tumors, and 484.9 days for connective tissue diseases.
(1) Infectious diseases accounted for 21% of those with fever for more than 3 months.
②The longer the time and the older the age, the greater the proportion of neoplastic diseases.
(3) The longer the time and the younger the age, the greater the proportion of connective tissue disease.
(2) The relationship between gender and age and etiology.
(1) In young women with unexplained fever, connective tissue disease and urinary tract infection are most often considered.
(2) In young people under 30 years of age, the proportion of connective tissue disease is higher, while it is less common in those over 70 years of age.
③ In those over 50 years of age, the proportion of malignant tumors is significantly higher, and the proportion of malignant tumors in young patients younger than 20 years of age is significantly lower.
④ Diseases with a higher incidence in women than in men mainly include lupus erythematosus, urinary tract infection, and extrapulmonary tuberculosis.
⑤ Diseases with more men than women mainly include malignant lymphoma, liver cancer, pulmonary tuberculosis, etc.
(3) The relationship between the number of visits and the cause of the disease. The diseases that could be diagnosed in the first visit were mostly infectious diseases (82%), the diseases that could be diagnosed in the second visit were partly rheumatic immune diseases (7%) and partly infectious diseases (85%), while the diseases that could be diagnosed after 1 week of admission were in the order of infection (43%), tumor (22%), rheumatism (21%), miscellaneous diseases and undiagnosed diseases (14%), and the diseases that could be diagnosed through follow-up observation after discharge Most of them were rheumatologic diseases (38%), followed by infections (10%), tumors (10%), miscellaneous diseases and undiagnosed diseases (42%); the proportion of diagnosed infectious diseases decreased with time, and nearly half of infectious diseases were diagnosed before admission, while other causes were mostly diagnosed after admission.
(4) The relationship between the effect of antipyretic and analgesic drugs and the etiology. For tumorigenic fever, there can be obvious antipyretic function and can be reduced to below normal; for connective tissue disease, the fever can be slightly reduced, but not to normal; for infectious fever, there is mostly no obvious effect. Sudden chills can also be caused when antipyretic agents are given to patients with recurrent hyperthermia, which is the result of compensatory muscle contraction after significant suppression of body temperature, and should not be confused with hyperthermia.
3.Category-related laws
(1) When considering infectious diseases, tuberculosis infection accounts for about half of the cases, common bacterial and viral infections account for about 1/3; other special types of infections; 1) tuberculosis infection is the most common among infectious diseases, atypical pulmonary tuberculosis and extrapulmonary tuberculosis have become a difficult point of diagnosis in FUO because of the difficulty in diagnosing the etiology, statistics show that among 198 cases of infectious diseases, 98 cases of tuberculosis in the order of species are 29 cases of pulmonary tuberculosis (1 case combined with Wegener’s granulomatosis); 21 cases of tuberculous meningitis; 11 cases of undetected tuberculosis; 8 cases of tuberculous pleurisy; 3 cases of hematogenous disseminated cornified tuberculosis; the rest were: tuberculous encephalomyelitis, hepatic tuberculosis, tuberculous peritonitis, pulmonary + abdominal tuberculosis, tuberculous pleurisy + pericarditis, tuberculous spinal arachnoiditis, tuberculosis + tuberculous encephalomyelitis tuberculosis of the kidney, tuberculosis of the lung + liver + peritoneum, tuberculosis of multiple plasma cavities, tuberculosis of the cornea + tuberculosis peritonitis, tuberculosis pleurisy + tuberculosis peritonitis, tuberculosis of the intestine + tuberculosis peritonitis, tuberculosis of both lungs + conjunctival peritonitis, tuberculosis of the abdominal lymph nodes, multicentric castleman’s disease with tuberculosis infection, tuberculosis + mycobacteria, tuberculous encephalomyelitis + tuberculous pleurisy, lymph node tuberculosis tuberculous pericarditis, and intestinal tuberculosis.
(2) Statistics show that among infectious diseases, common bacterial and viral infections are 35.4%; some of these patients had unremitting fever after treatment with multiple broad-spectrum antibiotics and improved after giving oral memantine, some patients had improved fever after adding amikacin drip, and the rest of the cases had improved fever after combined application of multiple antibiotics (including erythromycin), or occasional use of glucocorticoids, and may It is also necessary to pay attention to patients with more specific urinary tract infections, which mostly do not have typical symptoms such as urinary frequency, urinary urgency and painful urination, but can be manifested as intermittent fever, irregular long-term low-grade fever, and single urine culture results are often negative, and often require more than 3 times of urine culture after discontinuation of drugs to make a clear diagnosis; there is also the diagnosis of infective endocarditis, which is often easy to be misdiagnosed or missed due to atypical clinical manifestations and low positive blood culture rate. The diagnosis of infective endocarditis is often misdiagnosed or missed due to atypical clinical manifestations and low positive blood culture rate.
(3) Other specific infections are typhoid/paratyphoid fever, brucella infection, liver abscess, cholangitis, Plasmodium infection, pulmonary schistosomiasis, cerebral cysticercosis, toxoplasma infection and other parasitic infections in that order.
(4) When considering neoplastic diseases, hematologic tumors, especially lymphoma, are the most common, accounting for about 3/5 of neoplastic diseases; other tumors are lung cancer (combined with obstructive pneumonia), mesothelioma and primary liver cancer, prostate cancer, intestinal cancer, malignant tumors of neuroendocrine origin in the tail of the pancreas, right atrial tumor, chronic granulocytic leukemia, etc. The diagnosis of atypical lymphoma is difficult and can only be confirmed by biopsy of the affected area or repeated bone marrow aspiration, and sometimes by liver or spleen aspiration. In addition, the main reason for misdiagnosis of lung cancer as unexplained fever is the combination of obstructive pneumonia, therefore, for patients with pneumonia who have poor anti-infection treatment, the possibility of tumor must be considered.
(5) When considering connective tissue disease, adult Still’s disease has the highest proportion, accounting for about 51.5% of connective tissue and inflammatory vascular diseases, followed by systemic lupus erythematosus, Wegener’s granulomatosis, connective tissue disease of undetermined classification, systemic vasculitis, nodular disease and aortitis; therefore, among FUO caused by connective tissue and inflammatory vascular diseases, adult Still’s disease should be excluded first; its diagnosis The diagnosis of FUO lacks specific diagnostic indicators and is mostly based on existing diagnostic criteria such as Yamaguchi’s criteria, which require exclusion of other diseases such as infections and tumors; clinically, the diagnosis should be confirmed only after repeated bone marrow aspiration, biopsy and lymph node biopsy to exclude lymphoma and sepsis; sometimes the disease can develop into lymphoma and other diseases as it progresses, requiring long-term treatment and follow-up; in the elderly, giant cell In the elderly, giant cell arteritis accounts for the first place, accounting for 25.5% of all connective tissue diseases, nodular polyarteritis up to 17%, mixed connective tissue disease 15%, and dermatomyositis 11%.
(6) When other types of diseases are considered, the etiology is widely distributed, in the order of Crohn’s disease (17.4%), necrotizing lymphadenitis (13.0%), drug-related liver damage (8.7%), allergic pneumonia, periodic fever, chronic nonspecific lymphadenitis, central fever, mesencephalic syndrome, functional fever, drug-related fever, myelodysplastic syndrome, polycentric castleman’s disease, hypothalamic syndrome, left lower lobe bronchogenic granuloma, pulmonary lymphoma-like granuloma, left knee synovial chondrosarcoma, eosinophilic pneumonia, cold agglutinin syndrome, bronchiectasis, multiple myeloma, benign recurrent aseptic meningitis; drug fever (29.7%) and functional fever (12.7%) have also been reported, both accounting for 42.4% of the total number of other types of febrile illnesses. Patients with drug fever can be related to the use of unexplained herbal medicines, and patients diagnosed with functional fever mostly resolve their fever on their own within 3 months after consultation.
(7) Approximately 10% of patients with FUO cannot be diagnosed definitively, and about 96% of these patients younger than 35 years of age eventually resolve their fever, but only 68% of the elderly eventually resolve their fever; at least nearly one-third of patients with undiagnosed FUO have a poor prognosis and will die.
In conclusion, for patients with fever of unknown origin, the commonly used thinking methods are also these two: the characteristic thinking method (vertical thinking) and the probabilistic thinking method (horizontal thinking), both of which are often used in combination; the French philosopher and mathematician Pascal once said that man is only a fragile reed of nature, but it is a reed that thinks; therefore, in the diagnosis of such difficult diseases as fever of unknown origin, the application of philosophical thinking guides In the diagnosis of such difficult diseases as fever of unknown origin, it is important to apply philosophical thinking to guide clinical diagnosis, cultivate correct clinical thinking, and establish a correct way of thinking in order to clearly diagnose and find the cause of the disease.