This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Mr Chaturvedi a 70-year-old man comes to casualty with urinary retention and back pain. Which investigation should be performed - \nSelect and explain. \nA. Serum acid phosphatase, B. Serum Calcium, C. Serum alkaline phosphatase, D. Serum electrophoresis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: This pt. is suspected to have Ca Prostate as\nProstatic Ca is the most common malignant tumor in men over 65 yrs. of age.\nSymptoms of Bladder outlet obstruction and back pains (due to bony metastasis in the pelvis & lumbar vertebra) indicate towards prostate Ca.\nSerum acid phosphates is a tumor marker of prostate Ca.\nBut now serum acid phosphates assay has been superseded by PSA assay (Prostate specific antigen).\n\nProstate-specific antigen\n\n\nIt is a glycoprotein produced only in the prostatic cells (both benign & malignant). It facilitates liquefaction of semen.\nIt is neither sensitive nor specific for early prostate carcinoma (it is prostate specific and not prostate cancer specific), nevertheless it gives some help in making a diagnosis.\nNormal serum level\xa0→\xa0less than 4 mg/ml\n4 - 10 mg/ml →\xa0\xa0this range is common for both BHP and Ca.\nMore than 10 mg/ml\xa0→\xa0approx 75% will have cancer.\nSince PSA is not specific for Ca, PSA Velocity & PSA density is used to detect Prostate cancer.\nPSA velocity is the rate of change in PSA levels over time and is expressed most commonly as the PSA doubling time. For men with a PSA above 4, PSA velocity of more than .75 mg/ml year is suggestive of Ca. While for those with lower PSA levels, rates above 0.5 mg/ml, per year should be used to advise biopsy.\nPSA density is calculated by dividing the serum PSA by the estimated prostate weight (measured by TRUS). It was developed to correct for the contribution of BPH to the total PSA level.\nValues < 0.10 are consistent with BPH.\n> 0.15 suggest cancer', 'role': 'assistant'}]