Thursday, September 19, 2013


  We in medicine or even in the general conversation  often say that it is not a gospel truth. So what do we mean by that ? I have used the phrase in my explanation of test results or medical prognosis with the same phrase . But I have found out one fact , when a test is new it is more likely to be more accurate in diagnosis of a disease or predict prognosis . But as we get more experience , we realized that the test is not as good as we thought it to be .Every time a new test comes out we think it to be a gospel truth , but as we gain more data , the reliability of the test goes down . Take for example the test  called PSA . When we started doing it to diagnose the prostate cancer , we thought that it could diagnose the cancer i overwhelming cases , may be 95 %. Now that we have been doing it for long time we have realized that it is not as good and then we also know that at mild elevation it is less accurate than at very high elevated level .The story that I am going to tell , is one such case of high expectation that did not turn out to be true /
    I saw this 63 years old white female for abnormal X-ray . She was admitted with the diagnosis of the pneumonia . She was a smoker . She had cough for long time , which she had attributed to her smoking . But it persisted and then her primary care physician did a chest X-ray and it was reported to show pneumonia . She was started on antibiotics . The X-ray did not get better and so I was called in I did the CT scan and it was looking more like a mass than like pneumonia . I did the bronchoscopy and biopsy . I did not see any tumor when I did look inside , but I still did the biopsy . It did not show any cancer . She did not tolerate the procedure very well . Her oxygen saturation had dropped and she started wheezing and was quite short of breath . I had to give her medicines and nebuliser treatment .She had bad CO PD . I had discussion  with her I told her that I was quite concerned about cancer , but did not have the diagnosis . She seemed to have very  poor lung capacity and so was not a candidate for the resection of the tumor or do open biopsy .So the other option remaining to get the diagnosis was to consider a needle biopsy . Unfortunately the tumor was not at the edge of the lung and the 'chance ' of collapse of the lung with the biopsy . And she had hard time with the bronchoscopy ,she certainly could not have tolerated the collapse of the lung . So after the discussion we decided to do the follow up as out patient and do the PET scan , which was new at that time . The PET scan is a biological scan . When we do Ct scan , we are looking at the structure of the various organs. But does not tell us as to what is the abnormality . PET scan shows the metabolic activity . Every cell needs glucose for the metabolic activity . So in the PET scan glucose tagged with nuclear material is injected . The uptake of the glucose is more in the cancer cells or infection or inflammation. So depending upon the uptake we can diagnose cancer . So we did the PET scan . It was positive in the lung spot , suggesting that it was 'most likely ' cancer  But it also showed that there was uptake in the left breast . The lung tumor was in the right lung and the breast uptake was on the other side .. So one possibility was that she had breast cancer and it had spread to the lung . The PET scan was suppose to be great tool . in diagnosis of cancer , may be 95 % . In a way I was happy . Please note that some nodes in the chest was also  showing uptake . So if she had lung cancer it was not operable . The prognosis with unresected lung cancer is worse compared to breast cancer , as latter responds to the chemotherapy . I sent her to a surgeon .
     The surgeon called me in next couple of days . SHE DID NOT HAVE BREAST CANCER .  As it turned out to be , she had breast abscess and not a breast cancer . The pick up that we saw on PET scan was not due to cancer , but due to infection . So PET scan was not gospel truth and it fooled us . She did have lung cancer .    

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