Ref: American Society for Clinical Pathology
- Don’t perform population based screening for 25-OH-Vitamin D deficiency. Vitamin D deficiency is common in many populations, particularly in patients at higher latitudes, during winter months and in those with limited sun exposure. Over the counter Vitamin D supplements and increased summer sun exposure are sufficient for most otherwise healthy patients. Laboratory testing is appropriate in higher risk patients when results will be used to institute more aggressive therapy (e.g., osteoporosis, chronic kidney disease, malabsorption, some infections, obese individuals).
- Don’t perform low risk HPV testing. National guidelines provide for HPV testing in patients with certain abnormal Pap smears and in other select clinical indications. The presence of high risk HPV leads to more frequent examination or more aggressive investigation (e.g., colposcopy and biopsy). There is no medical indication for low risk HPV testing (HPV types that cause genital warts or very minor cell changes on the cervix) because the infection is not associated with disease progression and there is no treatment or therapy change indicated when low risk HPV is identified.
- Only order Methylated Septin 9 (SEPT9) to screen for colon cancer on patients for whom conventional diagnostics are not possible. Methylated Septin 9 (SEPT9) is a plasma test to screen patients for colorectal cancer. Its sensitivity and specificity are similar to commonly ordered stool guaiac or fecal immune tests. It offers an advantage over no testing in patients that refuse these tests or who, despite aggressive counseling, decline to have recommended colonoscopy. The test should not be considered as an alternative to standard diagnostic procedures when those procedures are possible.
- Don’t use bleeding time test to guide patient care. The bleeding time test is an older assay that has been replaced by alternative coagulation tests. The relationship between the bleeding time test and the risk of a patient’s actually bleeding has not been established. Further, the test leaves a scar on the forearm. There are other reliable tests of coagulation available to evaluate the risks of bleeding in appropriate patient populations.
- Don’t order an erythrocyte sedimentation rate (ESR) to look for inflammation in patients with undiagnosed conditions. Order a C-reactive protein (CRP) to detect acute phase inflammation. CRP is a more sensitive and specific reflection of the acute phase of inflammation than is the ESR. In the first 24 hours of a disease process, the CRP will be elevated, while the ESR may be normal. If the source of inflammation is removed, the CRP will return to normal within a day or so, while the ESR will remain elevated for several days until excess fibrinogen is removed from the serum.
- Don’t test vitamin K levels unless the patient has an abnormal international normalized ratio (INR) and does not respond to vitamin K therapy. Measurements of the level of vitamin K in the blood are rarely used to determine if a deficiency exists. Vitamin K deficiency is very rare, but when it does occur, a prolonged prothrombin time (PT) and elevated INR will result. A diagnosis is typically made by observing the PT correction following administration of vitamin K, plus the presence of clinical risk factors for vitamin K deficiency.
- Don’t prescribe testosterone therapy unless there is laboratory evidence of testosterone deficiency. With the increased incidence of obesity and diabetes, there may be increasing numbers of older men with lower testosterone levels that do not fully meet diagnostic or symptomatic criteria for hypogonadism. Current clinical guidelines recommend making a diagnosis of androgen deficiency only in men with consistent symptoms and signs coupled with unequivocally low serum testosterone levels. Serum testosterone should only be ordered on patients exhibiting signs and symptoms of androgen deficiency.
- Don’t test for myoglobin or CK-MB in the diagnosis of acute myocardial infarction (AMI). Instead, use troponin I or T. Unlike CK-MB and myoglobin, the release of troponin I or T is specific to cardiac injury. Troponin is released before CK-MB and appears in the blood as early as, if not earlier than, myoglobin after AMI. Approximately 30% of patients experiencing chest discomfort at rest with a normal CK-MB will be diagnosed with AMI when evaluated using troponins. Single-point troponin measurements equate to infarct size for the determination of the AMI severity. Accordingly, there is much support for relying solely on troponin and discontinuing the use of CK-MB and other markers.
- Don’t order multiple tests in the initial evaluation of a patient with suspected non-neoplastic thyroid disease. Order thyroid-stimulating hormone (TSH), and if abnormal, follow up with additional evaluation or treatment depending on the findings. The TSH test can detect subclinical thyroid disease in patients without symptoms of thyroid dysfunction. A TSH value within the reference interval excludes the majority of cases of primary overt thyroid disease. If the TSH is abnormal, confirm the diagnosis with free thyroxine (T4).
These items are provided solely for informational purposes and are not intended as a substitute for consultation with a medical professional. Patients with any specific questions about the items on this list or their individual situation should consult their physician.
Ref: American Society for Clinical Pathology
Released February 21, 2014 and February 4, 2015
Liquid Biopsy- Not just yet….!
Here is the answer to the question heard so often- Can a single blood test tell if I have cancer?
What is a liquid biopsy?
Ans: It has been found that some DNA (the multiplying nuclear material of a cell) floats around in the blood of all individuals. This is called cell free DNA (cfDNA) because this is no longer within the cell as such. Some times in patient with tumors, it is found that few tumor cells maybe wandering around in the blood. Scientists are now studying this DNA and the few tumor cells which maybe shed from the tumor into the blood and relating it to various cancers and diseases. Hence a blood sample for this DNA is being called a liquid biopsy although the terminology has been discussed as controversial by various scientific groups as it is not a biopsy in the true sense.
How does it differ from a routine biopsy?
Ans: Biopsy is a test involving removal of some amount of tissue involved with disease, its processing and the examination under the microscope by a pathologist for final diagnosis. Solid tissue biopsy tends to be invasive to varying degrees, depending on site of disease. Removal of representative diseased tissue and its examination under the microscope offers complete confidence of the test result.
A liquid biopsy is not a biopsy in the true sense because it does not include removal of firm solid diseased tissue. It is simply removal of blood for a test ( molecular genetic analysis) as is done while drawing blood samples of various tests in the routine.
Where is its use established?
Ans: This technique was initially researched for detection of prenatal diseases in a fetus. Presence of cell free DNA of the baby has been found in maternal blood. By doing molecular tests on the maternal blood, one could look for specific mutations known to be associated with abnormalities in babies. However it has not yet replaced the standard triple tests being done during pregnancy. Testing for cell free DNA could be of use in detecting various chromosomal disorders and diseases running in a family.
Is it routinely advised for prenatal diagnosis?
Ans: As of now it has not replaced the triple test. It maybe advised to rule out suspicion of a serious genetic disease which runs in the family and which increases the risk of a baby being born with the same disease. This test is also called Non invasive prenatal test (NIPT). There is a small chance of the test being false positive or false negative as the fetal cell free DNA is not exactly representative of the fetal karyotype. This test is usually done earlier (10 weeks) than the invasive amniocentesis (15.5 weeks). As per existing protocols, it is advised that a positive NIPT test should always be confirmed by amniocentesis later.
This test however has a potential of creating a paradigm shift in antenatal diagnosis.
What information does it provide about cancer?
Ans: Cancers, it has been found, release some degree of their DNA, called ‘cell tumor DNA (ctDNA) into the blood. This DNA is tested for genetic details e.g mutations specific for some tumors. In addition some tumor cells from cancers may also be released from the tumor. This could help in monitoring response to therapy and relapses after treatment. Presently it would be premature to say that this test can replace the routine tissue biopsy for cancer diagnosis.
What are the limitations of this test ?
Ans: Although, theoretically, this test appears an excellent replacement for invasive tissue biopsy diagnosis for cancer, presently it is not so. The tests need validation and standardisation of various assays. In addition, some tumors maybe heterogenous in the composition of their DNA in various parts. Hence, sole detection of a few mutations may not represent the true picture. Another problem is that these particles are in very miniscule amounts and may/may not be present at the time of sampling. The potential of this test has been extensively discussed in the recent United States and Canadian Academy of Pathologists, however the entire fraternity of medicine realise that the interpretation of the information that this test provides has yet to be deciphered, correctly interpreted and evidence based.
What type of a test is this?
Ans: This is a molecular/ genetic test and like most molecular tests, these are expensive and complex. The test for cancer targets circulating tumor cells and free DNA in the blood and further interpretation of the information received has to be carried out. Presently, although the concept is very exciting, the reliability of this test is low.
What does the future hold for this test?
Ans: The test appears very promising once it standardised and validated. The application of detecting cancer tumor cells and ct DNA for early detection is of public interest but the assays for this test presently lack sensitivity and specificity. Applying it to getting information as to how a patient with cancer shall fare can be deciphered in fair number of cancers, for eg breast cancer.
Presently detecting cfDNA (liquid biopsy) maybe of use in monitoring success of cancer treatment (leukemias and lung cancer) and for prenatal diagnosis. More research based evidence is required to use this test for routine screening.