Pneumonia: Diagnosis

by Jeremy Brown, PhD

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    00:00 So what are the principles of management of somebody who's presenting with what seems to be a community acquired pneumonia.

    00:08 Well first of all, you need to confirm the diagnosis, then you need to assess the severity, and then you need to think about treatment. That has three main components to it: correct the oxygenation, because that's the risk for mortality, treat the fluid balance again, hyportension is a risk for the patient, and three, clearly it’s an infection and you need to kill the pathogen and that’s going to require antibiotics. And then, you need to monitor to make sure the patient is improving with whatever management you've instigated.

    00:37 So to take these in turn, confirming the diagnosis. Essentially that's a chest X ray. You think the patient has some crackles over the right lung, and they are presenting with a fever, then you need to know whether there is a consolidation present, so do a chest X ray, and it might show lobar consolidation as it’s shown here in the right lower lobe in this chest X ray.

    00:57 It's also very important to do a chest X ray to look for complications, and we’ll discuss some of those later in this talk. But we are talking largely about pleural effusion and there may be related pathologies, so for example if you have a lung tumor which is blocking a bronchus then you'll get pneumonia distal to that obstruction quite easily, so a chest X ray might help identify patients who have coexistent pathology which is relevant such as a lung cancer. And also it will help confirm that there isn't another diagnosis present and that you've been fooled and that this is not a pneumonia, for example pulmonary edema, etc. Sometimes, you might need to do more extensive radiological investigations such as a CT thorax, or a CT pulmonary angiography, but that's unusual. And if you are really worried about heart disease, then you are going to need to do an ECG, echocardiogram.

    01:52 Now, blood tests are quite useful in patients with pneumonia because there are certain abnormalities that may show up. For example if somebody is going on acute infection you might expect the white cell count to go high, to be raised as an inflammatory response. That's true, it happens a lot in pneumonia, but also a low white cell count is also characteristic of infection in these patients as well. The urea and electrolytes can show significant abnormalities, but commonly a raised urea and a raised creatinine due to the degree of acute kidney injury, and often patients have a low-sodium as well, a hyponatremia.

    02:27 Liver function tests are often abnormal in patients with pneumonia, a high ALT and a high alkaline phosphatase, and the albumin is one of those markers of acute infection.

    02:38 So for example somebody gets acute pneumococcal pneumonia, their albumin may drop from its normal range, about 40 down to 25 very quickly, so hypoalbuminemia is a marker of infection.

    02:51 Possibly the most important blood test is the C-reactive protein. This is a marker of inflammation. So if you have pneumonia, its infection, there should be a very significant inflammatory response, so the C-reactive protein, which is normally less than five, goes up very rapidly in most patients with pneumonia. So if you have a C-reactive protein which is not gone, but above 40 you might want to think about the diagnosis in a bit more detail, because it may not be pneumonia. In fact, well it's not uncommon for it to be above 100, 200, and even 500, or 600 in patients with acute pneumonia. The other blood test we need to do are tests for oxygenation that I shall discuss later, and there are some blood tests, which are tests for potential infecting pathogens, which also I’ll discuss later. So, what’s the differential diagnosis of somebody who is presenting with what you might think is community acquired pneumonia? What we actually mentioned already acute bronchitis, influenza bronchitis are two of the main differential diagnosis. The important thing there is they do not normally have evidence of consolidation.

    03:52 If you have evidence consolidation, either clinically or on an X ray then that means the patient has a pneumonia rather than just a simple acute tracheobronchitis. Then there are range of common, non-infective respiratory diseases which really need to be considered if anybody presenting with an acute respiratory problem, pulmonary emboli, pulmonary oedema, acute respiratory distress syndrome, not that common but very important, and lung cancer.

    04:17 Now the top two, pulmonary emboli and pulmonary oedema, they are common causes of acute respiratory problems, and they are non-infective so that you should be able to distinguish in most patients with pneumonia from those, but if you look at the data, many patients with pulmonary emboli are misdiagnosed with pneumonia initially, and the same for pulmonary oedema. So that needs to be considered in a differential diagnosis. Lung cancer, because of its ability to cause infection distal to where our lung cancer may be obstructing the bronchus, needs to be thought about, especially in the patients who are over 50, who smoke. Just think that there may be a lung cancer underlying this problem, while the X ray shadowing you are seeing is not consolidation but a large tumor instead.

    04:58 ARDS is a subject of another lecture. It’s presents with bilateral consolidation, a marked hypoxia, and is actually a consequence of pneumonia frequently. It can also occur in situations without pneumonia and that's a relatively common presentation of bilateral consolidation, which might be confused with pneumonia in some certain circumstances.

    05:23 In addition, there are a range of relatively unusual and rare lung conditions, which cause inflammation and consolidation, or what looks like consolidation on an X ray. And these, because they cause inflammation and systemic upset, and have X ray changes suggestive of consolidation could easily be confused with pneumonia. Now fortunately, they are very rare but they do need to be considered in patients who are not improving. So these include diseases such as cryptogenic organizing pneumonia, a non-infective form of consolidation, pulmonary eosinophilia, that's where you get eosinophil forming consolidation in the lungs, allergic bronchopulmonary aspergillosis, which is a subject of one of the airways talks, hypersensitive pneumonitis and vasculitis, which are discussed in the interstitial lung disease talks, and the former vascular talks respectively. So for example this is a patient, a 40-year-old man, he's had two weeks of fever, and breathlessness, and the C-reactive protein shows there's quite active inflammation with a CRP of 222. Now, not unreasonably he is being treated with antibiotics because it's thought that he may have infection, a pneumonia, but he is not getting better, and in fact it turns out that he has a disease, and you can see this here, which is causing a eosinophilic infiltration, a consolidation in both lungs as outlined by these circles there. And, this disease is called pulmonary eosinophilia, and the treatment is required in these circumstances is corticosteroids, and with that he gets better. So this is an unusual disease but it’s an example of what could be confused as community acquired pneumonia. But I just have to re-iterate, these are rare diseases and they are only rarely considered in patients when they are not getting better with the antibiotics. Management. How do we assess the severity? And this is largely done using a score called the Curb65 score, and this takes the five factors of confusion, whether it’s present or not. A urea whether it’s greater than 7 or not. A respiratory rate whether it’s greater than 30 or not. A blood pressure with a diastolic blood pressure is less than 60 or not. And whether the patient is over 65 years of age or not. And that gives you a six point score, 0, 1, 2, 3, 4 or 5 and with that score that defines how severe, or defines the mortality, the chance of death occurring with that episode of pneumonia. So for example if you have a score of 0 or 1, the chance of death is less than 3% and that's very mild disease and most of those patients will be treated at home. When you get a score of 2, that's moderate in community acquired pneumonia and most of these patients will need to come in to hospital and you can see on this graph that the mortality of that is about 13 or 15%. It's quite significant. Then, as you go up the system, the mortality associated with the score becomes higher, so that with a higher score of four or five the mortality is around 50%, and those are the patients with severe disease that you really need to consider referral to intensive care for close and aggressive management. As well as the Curb65 score, there are other features that can be used, other clinical features that can be used to identify patients who may have more severe disease. So worrying features of those who are hypoxic despite having a high inspired oxygen concentration. Patients who seem to have bilateral disease or disease that spread during the hospital admission, despite the antibiotics. If somebody has a blood culture which is for an infective organism, that instantly places them into a group that has mortality of about 20%. The C-reactive protein, the blood marker for inflammation, if it’s particularly high, above 250, that seems to suggest patients who have an increased mortality in some data that has been published. And then, if you have a severe co-morbidity, if you have underlying cardiac disease, underlying COPD, or renal impairment then that is quite likely to decompensate because of the acute infection, and that would increase the risk of severe consequences of the infection. So just to go for a couple of examples, here is patient A, age 53, presents to casualty with feeling of cough, and phlegm, and fever for the past three days. He is not confused, urea is was actually slightly high with a 9, but not terribly breathless, blood pressure was normal, that gives a CURB65 score of 1, just for the urea alone, the rest of them were normal, so that's a 3% mortality, they are not hypoxic, chest X ray confirmed pneumonia but actually they could be treated at home with some oral antibiotics. Patient B, on the other hand, 67 years of age, so he gets a point for that, he is confused, he gets a point for that because normally they are not confused. Urea of 10, so he gets a point for that. And he is breathlessness, respiratory rate is 30, so gets a point for that. Does not have a hypertension so he doesn't get a point for that. Now it gives a Curb65 score of 4, and that suggest mortality of about 42% for this sort of patient. In addition, I'm going with his respiratory rate being above 30. The PaO2 was low - it was about- is less than 8 despite being on 60% oxygen, and there is bilateral consolidation. So this is a severe disease markedly hypoxic.

    10:55 The patient needs to go to an intensive care, and probably needs to be intubated, or at least if there is not any easy quick response to high flow oxygen, they will need to be intubated and ventilated because of their marked hypoxia. And in this situation that patient actually survived, although given the severity of illness it was touch and go.

    About the Lecture

    The lecture Pneumonia: Diagnosis by Jeremy Brown, PhD is from the course Infections of the Respiratory Tract.

    Included Quiz Questions

    1. It is required for prognosis
    2. It is required for identifying consolidation
    3. It is required to check for complications
    4. It is required for excluding tumors
    5. It is required for other differential diagnosis
    1. Creatinine < 40
    2. Low sodium
    3. High WBC count
    4. High urea / creatinine
    5. Low albumin
    1. Clear lung fields on chest X-ray
    2. High WBC count
    3. Low glucose levels
    4. Low albumin levels
    5. High urea and creatinine levels
    1. Pulmonary eosinophilia
    2. Pulmonary embolus
    3. Pulmonary edema
    4. ARDS
    5. Lung cancer
    1. C-reactive protein less than 40
    2. Spreading consolidation
    3. Septicemia
    4. Severe comorbidities
    5. Oxygen saturation less than 92%
    1. Treat at home
    2. Doesn't require treatment
    3. Admit and treat the patient
    4. Consider ITU referral
    5. Admit in the ICU
    1. Respiratory rate < 30 per minute
    2. Confusion
    3. Urea > 7 mmol/L (19mg/dL)
    4. BP < 60 mm Hg diastolic
    5. Age > 65 years
    1. - Confirm the diagnosis - Assess the severity - Correct oxygenation and fluid balance - Kill the pathogen - Monitor progress
    2. Assess the severity - Correct oxygenation and fluid balance - Kill the pathogen - Monitor progress - Confirm the diagnosis
    3. - Correct oxygenation and fluid balance - Kill the pathogen - Monitor progress - Confirm the diagnosis - Assess the severity
    4. Kill the pathogen - Monitor progress - Confirm the diagnosis - Assess the severity - Correct oxygenation and fluid balance
    5. - Monitor progress - Confirm the diagnosis - Assess the severity - Correct oxygenation and fluid balance - Kill the pathogen
    1. Pulmonary eosinophilia
    2. Lobar pneumonia
    3. Interstitial pneumonia
    4. Influenza
    5. Upper respiratory tract infection
    1. 20%
    2. 10%
    3. 5%
    4. 50%
    5. 1%
    1. CURB-65 is a 5 point score
    2. The risk of mortality of the patient increases as the CURB-65 score decreases
    3. The CURB-65 score is the only method of assessing mortality in a patient with pneumonia
    4. The CURB-65 score uses oxygen saturation as an important parameter in deciding a score
    1. 3
    2. 4
    3. 5
    4. 2

    Author of lecture Pneumonia: Diagnosis

     Jeremy Brown, PhD

    Jeremy Brown, PhD

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