THM1) Usually a chest X-ray is done in full inspiration. Ask for an X-ray chest in expiration when you want to pick up subtle miliary TB or a small pneumothorax.
THM2) Serum alkaline phosphatase rises in liver and bone diseases. In liver, it rises in cholestasis & space occupying lesions. In bones it rises, importantly, in metastatic bone diseases. That said, the commonest cause of elevated alkaline phosphatase is vitamin D deficiency.
THM3) If a patient with fatty liver or one who consumes alcohol has thrombocytopenia, do a full liver profile and investigate for cirrhosis.
THM4) Some other tumor markers-
a] CA 19-9: Pancreas
b] Thyroglobulin: Thyroid
c] hCG: Testes, choriocarcinoma
d] CEA : Colon/Rectum
e] HER2/neu, CA 15-3: Breast
THM5) Never ever get Widal test done. Not only is it nearly useless, it also is misguiding. Prefer getting blood cultures before you give antibiotics.
THM6) Combinations that can cause hyperkalemia-
a] Potassium sparing diuretics + ACEIs or ARBs.
b] ACEIs + ARBs eg. Ramipril + Losartan
c] Liq. KCl + any of the above.
THM7) If two thalassemia minors get married, intranatal testing at 12 weeks (chorionic villous sampling) or at 20 weeks (foetal blood) will diagnose thalassemia major (chance of which is 25%). May recommend termination of pregnancy if thalassemia major is detected.
THM8) Leptospirosis shows leucocytosis with thrombocytopenia. Rise in bilirubin is disproportionate to rise in SGOT/SGPT. Serum levels of creatinine, CPK & LDH may also be raised.
THM9] Get vitamin B12 tested in these clinical situations:
- Stomatitis if recurrent
- Anemia with high MCV
- Nausea, vomiting & weight loss
- Generalized Anxiety Disorder
- Lack of memory or concentration
- Irritable bowel syndrome
THM10) HRCT thorax (without contrast) is done for suspected parenchymal diseases like interstitial lung disease, bronchiectasis, pneumonia etc.
Contrast CT Thorax is done to enhance tumors or nodes, eg. mediastinal masses. Thus, if doing a CT Thorax for suspected TB, get a contrast scan.
THM11) Of the common blood tests the ONLY ones requiring fasting are triglycerides and fasting sugar. ESR, TSH, uric acid, cholesterol do not require fasting. Yes, even serum cholesterol can be done non-fasting.
THM12) Three diseases which tests may not pick up in the first few hours
1. Pneumonia on X-ray chest
2. Myocardial infarction on ECG
3. Cerebral infarction on CT Scan
THM13) A portable X ray is an A-P view instead of the standard P-A. This causes the heart to appear larger (pseudo-cardiomegaly). An expiratory film also does this.
THM14) A blood test to diagnose congestive heart failure is pro-BNP (brain natriuretic peptide). Level more than 400 pg/ml suggests is abnormal. In LVF or CCF, the levels are usually in thousands.
THM15) A 24-hour urinary uric acid measurement helps in deciding long term use of allopurinol or febuxostat. If the 24 hour excretion exceeds 800 mg, it is useful to use a drug to lower serum uric acid.
THM16) High dose vitamin C can cause false negative test for stool occult blood. Oral iron causes black stool but rarely causes a false positive occult blood test.
THM17) Following are some approximate radiation exposures (in milli Sv).
HRCT CHEST 1.0
CT ABD/PELVIS 2.0
CORONARY CT 4.0
CONVENTIONAL CAG 4.0
WHOLE BODY PET CT 8.0
THM18) Myalgias & a high total CPK can occur in uncontrolled hypothyroidism. Hence it may get difficult to gauge muscle toxicity of a statin in such patients.
THM19) When asking for CRP, ask for “CRP in mg/L” as CRP reported as POSITIVE or NEGATIVE is useless. Normal CRP is 0.2-3.0mg/L.
THM20) Serum ACE has fair sensitivity but poor specificity in diagnosis of sarcoidosis. It is quite useful in ocular sarcoid where biopsy is not possible. In sarcoidosis, ACE levels are directly related to number of organs affected & activity of granulomas. As disease progresses to fibrosis, levels decline.