There are generally three links in the process of disease diagnosis: ① investigation and research, collecting complete and accurate diagnostic data; ② Comprehensive analysis of data to establish a preliminary diagnosis; ③ If necessary, other relevant examinations and dynamic clinical observation will be carried out to verify and correct the diagnosis. Disease diagnosis must have extensive and profound medical knowledge, otherwise some diseases will be unknown; In addition, we should constantly accumulate clinical experience so that we can have a clear idea when dealing with problems, but we should avoid preconceptions when dealing with problems. The process of disease diagnosis is roughly as shown in the figure.
First, the collection of disease diagnosis data.
The first-hand diagnostic data collected by clinicians from examining patients is the most valuable information. When investigating and studying diseases, materials must be comprehensive and practical, which is one of the main keys to correct diagnosis. One-sided or wrong materials are common causes of misdiagnosis. Clinical data come from the following three aspects:
1. Complete medical history The medical history described by the patient may appear disorganized and fragmented. If the doctor takes the medical history subjectively, the collected medical history must be one-sided and superficial. One-sided and inaccurate medical history will cause serious diagnostic errors and must be avoided. For example, a patient with lobar pneumonia in the right lower lung has pain, jaundice, chills and fever in the right upper abdomen as the main symptoms, but his cough is mild, so he only complains of pain, chills and fever in the right upper abdomen when he sees a doctor, without mentioning cough; If doctors are subjective and one-sided, they may mistakenly focus on "acute cholecystitis" and ignore lobar pneumonia. General items in the medical history, such as age, sex, marriage, hobbies, menstruation, occupation, disease area, season, etc., can also be closely related to the disease, and we should also face it squarely. For example, if a female patient with ruptured ectopic pregnancy ignores her marriage history and menstrual history, it is easy for doctors to miss diagnosis. In order to get a complete medical history, it is necessary to patiently listen to the introduction of the patient himself, his family members, people who know the condition and doctors who have treated him in the past, and even go to the scene of the patient's illness to fully understand the whole process of the condition, so as to obtain a complete and reliable medical history.
2. The physical examination must be systematic and comprehensive, and the patient's cooperation should be obtained to prevent important omissions. For example, a patient with acute abdomen, the doctor repeatedly checked his chest, abdomen and back, and found no abnormality, which led to misdiagnosis; After careful examination, it was found to be inguinal incarcerated hernia. The reason for the delay in diagnosis is that the physical examination is not comprehensive and the necessary examination for acute abdomen is omitted. Misdiagnosis caused by physical examination negligence is not just an individual case in clinic.
3. Laboratory inspection and instrument inspection Laboratory inspection and instrument inspection should be carried out purposefully in combination with clinical manifestations. First, we should choose an effective and simple inspection method. When arranging the examination, the following points should be considered: ① What is the specificity of this examination? ② What is the sensitivity of this test? ③ Is the timing of inspection and specimen collection appropriate? Can it be carried out according to the specified requirements? ④ Specimen transportation. Are there any errors during the inspection? ⑤ Does the patient's physical strength, the ups and downs of the illness and the treatment of diagnosis and treatment affect the examination results? ⑥ For examinations that may burden patients, such as bronchography and some stress tests, we should also weigh the pros and cons and consider whether patients can accept them.
The results of laboratory examination and instrument examination must be comprehensively considered in combination with clinical conditions in order to make a correct evaluation. It is necessary to prevent the wrong practice of relying on laboratory inspection or instrument inspection for diagnosis. Therefore, doctors should pay attention to the specificity of the test results, the false positive and false negative of the test results. For example, the positive determination of serum alpha-fetoprotein has high specificity for the diagnosis of primary hepatocellular carcinoma, but there are still a few primary hepatocellular carcinomas that are still negative (false negative) until the end of their lives; On the other hand, some non-liver cancer diseases may appear serum AFP positive (false positive). In fact, the negative results of laboratory and instrument examination only show that there is no positive finding in this examination method, which does not mean that the subject absolutely does not exist or denies the existence of the corresponding disease. Due to timing or technical reasons, the negative results of the first or second laboratory or instrument examination are often not enough to rule out the existence of diseases. Such as nephritis proteinuria, diabetes hyperglycemia, plasmodium in malaria blood tablets, etc. , can appear intermittently; Negative results of throat swab examination for diphtheria and sputum tuberculosis are even more difficult to deny related diseases. On the other hand, typhoid or dysentery bacilli are found in fecal culture, which can also be seen in healthy carriers; The titer of Widal's test can also be increased in some acute febrile diseases. Other findings, such as lung shadow found by X-ray examination and abnormal waveform found by ultrasound examination, must be combined with medical history, physical examination and other related examinations to make a correct judgment.
The rapid development of modern diagnostic technology has given great help to clinicians. Mainly in the following aspects:
(1) Invention and improvement of endoscopes: All kinds of fiber endoscopes, such as fiber gastroscope, fiber colonoscope and fiber bronchoscope, are new products with small caliber, high flexibility and safe and convenient operation, which can be matched with accessories for corresponding diagnosis and treatment.
(2) Application of rapid ultra-micro biochemical analysis technology: such as enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (immunofluorescence assay; IFA) and other methods. Specific monoclonal antibody diagnosis technology has also been applied in clinic.
(3) the progress of image diagnosis technology, such as B-mode ultrasonic scanning and computerized tomography; ; CT), magnetic resonance imaging (magnetic resonance imaging; MRI) has been applied in clinic. CT and MRI have made gratifying breakthroughs in the diagnosis of intracranial, mediastinal and deep abdominal diseases. MRI plays an outstanding role in the diagnosis of cerebrovascular diseases and posterior cranial fossa lesions.
The application of these new diagnostic techniques has greatly enriched the contents of diagnostics and solved many clinical problems. In addition, in order to make clinicians understand the diagnostic and differential diagnostic significance of laboratory tests, the author added the chapter "Differential diagnostic significance of main laboratory tests" for clinicians to refer to when using laboratory test methods correctly.
Instrument inspection can be divided into two categories: non-invasive (non-invasive) and invasive (invasive). In principle, non-invasive examination should be adopted first. Only when the diagnosis of the disease cannot be confirmed by non-invasive examination, and only when there are clear indications and no contraindications, can we choose invasive examination.
Because the advanced diagnosis technology has not been popularized at present, the diagnosis of most common diseases does not need complicated technology, so we must pay attention to the basic skills of detailed medical history and comprehensive physical examination when diagnosing diseases, and combine routine examination with simple instrument examination to diagnose most diseases.
Second, establish diagnosis and verify diagnosis.
(A) collation of data, the establishment of diagnosis
1. Try to find the main diagnostic basis.
Clinicians should screen, sort out and measure which are primary and which are secondary from the data obtained from the investigation, carefully examine and verify the suspicious materials, and then comprehensively analyze the main verified materials to find out the relationship between them, and further speculate on the possible location (system or organ), nature and reasons of the lesions, so as to lay a good foundation for establishing a correct diagnosis.
Some diseases can have quite unique "special symptoms", such as butterfly erythema of systemic lupus erythematosus, eschar of tsutsugamushi disease, extraoral genital triad of Behcet's disease, measles mucosal plaque, acromegaly, Cushing's syndrome and so on. These "special symptoms" have important diagnostic significance.
When the typical symptoms of some diseases have been fully revealed and a group of symptoms reflecting the essence of the disease have appeared, it also has great diagnostic value. If the patient has staged fever, relative bradycardia, rosacea, splenomegaly, leucopenia with relative lymphocytosis and eosinophilia, a clinical diagnosis of typhoid fever can usually be made and further examination can be made to confirm the diagnosis. Another example is a young female patient with irregular fever, joint pain, hepatic and renal insufficiency, moderate anemia in hemogram, leukopenia, hematemesis and accelerated erythrocyte sedimentation rate. She can make a quasi-diagnosis of systemic lupus erythematosus, and further make lupus cell examination and antinuclear antibody determination to confirm the diagnosis.
The manifestations of diseases are various, and in many cases, there are "the same disease with different symptoms" or "different diseases with the same symptoms". For example, most patients with acute myocardial infarction show typical precordial pain, but they can also show epigastric colic similar to gallstones, or even no pain, showing shock or acute congestive heart failure, which belongs to the same disease and different diseases. Another example is tuberculosis, systemic lupus erythematosus, malaria, leptospirosis, syphilis, Behcet's disease, multiple myeloma, malignant reticular cell disease and so on. It may have many different clinical manifestations and imitate many different diseases. If you don't pay attention, it may lead to misdiagnosis or missed diagnosis. These are also examples of "the same disease but different symptoms". On the other hand, if hepatomegaly can be seen in some parasites or bacteria, viral diseases can also be seen in liver cirrhosis, liver cancer or other liver diseases, which is "the same disease and different disease". For example, amebic liver abscess was misdiagnosed as liver cancer and purulent pericarditis as liver abscess. Mild thalassemia mistaken for chronic viral hepatitis is a prominent example. This situation is sometimes encountered in clinic. If a doctor wants to distinguish, he must make a differential diagnosis of the disease.
In the early stage of the disease, when there is no "special symptom" that can be clearly diagnosed in complex or atypical cases, the following methods should be adopted: according to a main symptom (such as hypertension, edema, hematuria, etc. ), or several important symptoms should be combined into a syndrome (such as obstructive jaundice, hemolytic anemia, etc. ), and then put forward a group of diseases that may be identified for mutual identification. When putting forward a group of diseases that need to be identified, we should consider all possible diseases as much as possible to prevent serious omissions from leading to diagnostic errors, which requires doctors to consider the problems comprehensively. However, comprehensiveness does not mean rambling, but starting from the actual clinical data, grasping the main contradiction, putting forward a group of diseases with similar clinical manifestations, and with the deepening of analysis, comparing with each other, eliminating the less likely diseases one by one and narrowing the scope of differential diagnosis until one or more diseases with the greatest possibility remain. This is commonly known as "exclusion diagnosis" in clinic.
In the differential diagnosis of a group of diseases, it is necessary to affirm or deny each disease in the group. Its method is to distinguish other inconsistent similar diseases according to the special points of a disease itself, so as to achieve a correct understanding of the disease. The special features of diseases are generally summarized in the form of "diagnostic basis". On the one hand, "diagnostic basis" includes "special symptoms", which only appear in this disease and do not appear in other diseases; On the other hand, it also includes some symptoms not only found in the disease. When these symptoms coexist with "special symptoms", the reliability of "diagnosis basis" can be strengthened. The "diagnostic basis" is summarized from practice, which can generally reflect the nature of the disease, but the manifestations of the disease are varied and may not be completely consistent with the "diagnostic basis". Therefore, when using the "diagnostic basis", we should closely link with reality and oppose takenism and mechanism. It is necessary to shake the comprehensive examination data, refer to the "diagnosis basis" and analyze the condition properly in order to get the correct diagnosis. For example, one of the "diagnostic basis" of acute perforation of gastric and duodenal ulcer is that X-ray shows free gas shadow in nasal septum. However, in some cases of gastric and duodenal ulcer perforation, X-ray examination may not be able to detect the free air shadow under the diaphragm. On the other hand, in the case of intestinal gas cyst, the subphrenic free gas shadow can also be seen on abdominal X-ray film, which is often complicated with gastroduodenal ulcer and sometimes misdiagnosed as acute perforation of ulcer. Therefore, patients with acute abdomen should not rashly rule out the possibility of ulcer perforation because they have not found the subphrenic gas shadow, but think that it does not fully meet the requirements of "diagnostic basis", or do it for patients with gastroduodenal ulcer just because they have found the subphrenic gas shadow. Clinicians should carefully weigh the comprehensive examination materials, and sometimes they need close dynamic observation to make a final conclusion.
2. How to deny a disease?
If a disease to be diagnosed cannot explain all the main clinical manifestations of the patient, or lacks the expected' special symptoms', then the possibility of this disease is very small or can be denied. In the former case, for example, the patient has hematuria, bladder irritation, positive tuberculosis urine culture, and X-ray signs of worm-like defect shown by intravenous pyelography, hemorrhagic pyelonephritis can be ruled out, because hemorrhagic pyelonephritis can not explain the latter two symptoms, but renal tuberculosis can be completely explained. In the latter case, for example, a patient with precordial pain is suspected to be an acute myocardial infarction, but the electrocardiogram is always normal after repeated examination within three days, and there is no erythrocyte sedimentation rate and aspartate aminotransferase increase, so the existence of acute myocardial infarction can be denied. However, it should be noted that some diseases have no "special symptoms", or "special symptoms" only appear at a certain stage of the disease, and may not appear or have disappeared when doctors make a diagnosis and treatment, such as pericardial fricative sound in dry pericarditis.
3. How to identify a disease?
If the disease to be diagnosed can explain all the main clinical manifestations of the patient, and the "special symptoms" that should be seen in the top stage of the disease have been found, for example, it is found that the blood culture of the patient to be diagnosed with typhoid fever is strongly positive for typhoid Bacillus or serum typhoid Bacillus agglutination test, or lupus cells or high titer serum antinuclear antibodies are found in the blood of the patient to be diagnosed with systemic lupus erythematosus, the diagnosis of each disease can be determined. On the other hand, when encountering diseases lacking "special symptoms", a group of clinical syndromes with clear diagnostic significance can also play a role similar to "special symptoms", but their reliability is not as good as "special symptoms". For example, the syndrome consisting of fever, joint pain, acute myocarditis, accelerated erythrocyte sedimentation rate and increased serum anti-streptolysin "O" titer can be roughly diagnosed as rheumatic fever, but sometimes it can be confused with other connective tissue diseases.
In the process of differential diagnosis, after screening, there are several more likely diseases, which need the doctor to finally confirm the most likely disease. At this time, we must pay attention to the following points:
(1) When choosing among several possible diseases, common diseases, local frequently-occurring diseases or diseases prevalent at that time should generally be considered first. As for rare diseases, we should also consider them, but only when the clinical manifestations of patients can not be satisfactorily explained by the above diseases can we consider them.
(2) Don't make a diagnosis of neurosis easily when there is no sufficient diagnosis basis for the patient's disease.
(3) Consider the treatable diseases first, and then consider the incurable or refractory diseases.
(4) When a certain "special symptom" cannot explain all the important clinical phenomena of a certain disease, it is necessary to consider that the patient has two or more diseases at the same time or has complications.
(2) Clinical observation and diagnosis verification
Disease is a fast or slow pathological process. In this process, some clinical manifestations appear, others may disappear, or one disease is cured and another appears again. Therefore, it is necessary to analyze and diagnose it from the perspective of development. Doctors can only see the cross-section of a patient at a certain stage in the whole process of the disease, and often need to synthesize multiple cross-sections to understand the more complete face of the disease. This dynamic observation is helpful for the diagnosis of diseases that cannot be ruled out or confirmed for the time being. Such as herpes zoster and measles, it is not easy to diagnose until you see a rash; Suspected acute myocardial infarction patients with no specific changes in ECG at that time can often be identified by continuous observation for several days and other related examinations; Dynamic observation of fever types is very helpful for the diagnosis of malaria, relapsing fever and other diseases.
Correct understanding often needs to be achieved through repeated practice. Clinicians can come to an end after investigating, collecting and sorting out data and establishing a diagnosis. But the work is not over yet. The more important step is to carry out reasonable treatment according to the diagnosis, and the treatment effect in turn verifies the diagnosis. If the treatment is carried out according to the diagnosis and the expected curative effect is obtained, then, generally speaking, the diagnosis work is completed. On the other hand, it is also limited by the level of understanding and technical conditions to varying degrees in practice. In this case, it is common to partially and completely modify the original diagnosis. Some difficult cases often need in-depth dynamic observation, repeated examination and even diagnostic treatment to get a correct diagnosis. It must be emphasized that in order to guide the prevention and treatment work in time, especially for the acute and severe cases, before the clinical data is not enough to establish a definite diagnosis, the most likely diseases should be found out, treatment measures should be taken as a temporary diagnosis, and in-depth examination should be carried out at the same time, instead of just staying on the diagnosis problem, thus delaying the treatment opportunity.