Things you don't need to know…
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Things you don't need to know…
July 21st, 2012, 03:54
Originally Posted by
Then who can you blame?
Extreeeemingly long rant coming. I haven't checked for spelling errors, very likely there are a few of those. I'll do that tomorrow.
Finding the correct diagnosis can be very difficult, especially when
1. The disease has few or no characteristic symptoms
2. The disease can manifest itself in different ways, some of them atypical
3. The patient show few or no specific symptoms. This is especially true at the onset of disease.
4. The patient is unable to describe his/her symptoms. This is often the case with small children. Thus pediatricis is very much like a veterinary medicine, without the possibuility of euthanizing the patient.
5. The disease is uncommon.
A couple of examples:
If your patient has been exposed to an angry/frightened cat, and show symptoms like fever and general swelling of lymph nodes, cat scratch fever is faaaaar more likely than a diseas for which there have been 3 cases in Oregon the last 17 years. If there are no specific symptoms of plague, and you live in Oregon there is no rational reason to spend resources on looking for that disease. And if we did, there are very likely a huge number of other rare diseases we should look into as well. We can leave that for the patients where the disease don't develop as expected. Like they did in this particular case.
In a patient with infarction of the heart,we typically find
- pain in the middle of the chest, radiating to the neck and both arms
- signs in the ECG, which changes over a period of 5 days or so
- elevated levels of specific enzymes, sedimentation rate and white blood cells, which changes over a period of 5 days or so
But for some patients (quite a few) none of these symptoms are present, or they don't show until a couple of days later.
Some diseases can mimic a number of other illnesses. Two examples: Tuberculosis and SLE (Systemic lupus erythematosis) which is a rheumatic disease. They can both imitate a lot of chronic diseaes (like the thing"?). In cases like that, diagnosis is often reached by exclusion, we have to carefully eliminate a number of other possible diagnoses until one remains. It's a cumbersome, tme consuming and very demanding process.
Rheumatoid arthritis typically show symmetric pain, stiffness and swelling in finger joints and the root of the hand, toes, elbows and knees. These symptoms are chronic, typically lasting more than 3 months. In addition the patient may also show signs of general inflammation: fever, lethargy, elevated sedimentation rate and white blood cellcount. But it can take more than a year before typical symptoms arise. The disease can start with:
- typical symptoms from the start
- acute inflammation of one joint, no symmetry
- chronic inflammation of one joint, no symmetry
- acute inflammation of tendons, no arthritis
- pain and stiffness i muscles, no arthritis
- general inflammation symptoms, no localizing symptoms at all
- don't get me started on children.
Additionally, symptoms may come and go, especially in the beginning.
Acute appendicitis is a common disease, and should be easy to discover, right? Wrong, or rather, not necessarily. Typically the patient complains about abdominal pain, in the beginning localized centrally. Over time (a day or so) the pain wanders downwards to the right groin, and we find localized tenderness and spasms of the abdominal muscles there. And fever - but that is a very unspecific symptom. At the early stages there are few symptoms making appendicitis stand out, and it's easily overlooked. And, if the appendix lies behind the colon, local symptoms may be missing almost completely. I know, that happened to yours truly, and the appendix had perforated before they employed their knives.
Additionally, there are three conditions which can be indistinguishable: Acute inflammation of the fallopian tube (salpinx, the tube transporting egg cells from the ovaries to the uterus), inflammation of lymph glands in the area, and Crohn's disease, a chronic inflammation of the intestines which may be slumbering before abruptly becoming more aggressive. None of these conditions require acute surgery, acute appendicitis does. Since every operation is more or less risky, unneccessary surgery is bad. People die during or after even very simple procedures.
So what can we do about this?
More tests? Quite often not a good idea because
1. There may be no reliable tests available. A CT scan or ultrasound may or may not show signs of disease. If we find signs like thickening of the appendix, and the patient shows symptoms compatible with appendicitis, the patient probably has appendicitis. If there are no signs, we're back where we started, we know nothing more than we did before the test.
2. Some tests are in itself risky. CT scans expose patients to high doses of radiation, modern equipement often more so than older machines. Xrays of intestines and blood vessels are other high radiation procedures. It makes sense performing these examinations when there is a well defined reason for it, they should not be done just to be sure.
A biopsy can be very helpful. But there is also the risk of internal bleeding after the procedure, as well as infection. Again, if there is a defined reason behind performing a biopsy, the benefits outweigh the risks. But not if we don't expect to find anything.
3. Tests can be misleading.
First of all, perfectly normal (healthy) individuals may show abnormal results in tests. In fact, we prefer not to use the term normal values anymore because of this. In stead we use the term reference values, which means that around 95% of healthy individuals show results within that range. But this also means that 5% of healthy individuals have values outside these borders. And, roughly speakiing, it also indicates that if you run a number of tests (20 or more) it's not unlikely that some of them show seemingly pathological values.
Then there is the question of sensitivity and specifity. Sensitivity describes how good the test is at catching the patients, the sick ones. Specificity describes how well the test excludes the healthy ones. Unfortunately these two parameters are reciprocally related. The more sensitive a test is, the higher the risk of including healthy individuals among the patients (false positives). And the more specific a test is, the more people with disease are wrongly excluded (false negatives).
One example: In Norway we regularly examine the breasts of women older than 50 radiologically (mammography). We believe we by this detect more cancers at early stages, thus improving results of therapy. Additionally, detecting cancer early, we may avoid mutilating procedures like removing the entire breast and lymph nodes in the arm pit. These claims are disputed. No matter what, around 30% of the women have temporary signs of cancer, signs which will disappear. Unfortunately we are not able to indentify these women, which means that we unneccesaily operate on quite a number of women.
4. Cost. Many procedures are very expensive. Performing unneccessary tests is costly. Whether health care is financed by the government, insurance companies or the patient him/herself, this means that we get less health care for the money we spend.
Sometimes wait and see is the way to go. For instance, in a patient with anemia, in most cases the cause is iron deficiency. Iron deficiency is much more common than any other factor. So, unless there are other symptoms suggesting another diagnosis, we don't have to perform further tests. Just start treatment with iron, and examine the patient again after 2-4 weeks. If iron deficiency is the cause, we will see an increase in hemoglobine levels. If there's no improvement, or the levels are falling, then it's reasonable to examine the patient more closely.
Another example. Dyspepsia is (from Wikipedia) "characterized by chronic or recurrent pain in the upper abdomen, upper abdominal fullness and feeling full earlier than expected when eating". 97% of patients with this symptom have irritation or a superficial inflammation of the mucosa in the stomache and/or initial part of the intestines. 2% have an ulcer (probably less today). 0,5% have cancer. Gastroscopy, where we examine the stomach using fiber-optics, and if necessary take samples of the gastric and intestinal mucosa, is fairly reliable. But it's time consuming, and we can't examine every dyspeptic patient this way. In stead we'll treat the patients with drugs (several types), and examine the patient again after for instance 14 days. A patient with cancer won't improve, the others will most likely. The prognosis won't be affected by a 14 days delay.
OK, I assume it's been difficult reading all this drivel. Let me assure you that it can be just as difficult finding a correct diagnosis, even for trivial and quite common diseases.
pibbur who is somewhat exhausted by writing this. And who fears that some of his words are not commonly used in English (please tell me if there is something you don't understand, and I will explain). And who rrealize that it's far beyond time to go to bed. No Secret World tonight. *sighs*
Last edited by pibbur who; July 21st, 2012 at
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