TB screening

[skepticdoc]

I am sure all have heard of the XDR TB patient.

It worries me that it was diagnosed by accident, after an abnormal CXR ordered to evaluate some rib injury?

I am familiar with Dr. Roizen's (Oprah's buddy) arguments against routine pre-op CXR, but what would be the risk benefit analysis of TB screening CXR for:

the general population

college students that are going to share close quarters

Prison guards

Healthcare workers (please include doctors!)

Homeless people that visit the ER (all ER visits?)

Should we request a liberalization of coverage criteria for a "routine" CXR?

Routine screening is not indicated in the US due to the extremely low prevalence of the disease in the general population. In select high risk populations e.g. health care workers, it may be. Most health care workers - including physicians - receive a PPD annually.

That is not a solution for low-compliance patient populations. Neither are chest xrays, which are time consuming and insensitive to early disease.

We use an antigen-antibody rapid cassette test overseas, 10-minutes and one drop of whole blood later & we have results able to detect both latent & active TB. We have a data base of over 1000 patients that have been screened with this test, and with CXR's, and the blood test is far more sensitive, specific, and faster than the CXR.

The a-a tests currently approved for use in the US are equally sensitive & specific, but a bit slower due to processing methods, and more expensive.

Never the less, well proven rapid diagnostics are available, and approval for them to be used in the US should be sought & encouraged.

I am concerned that we are missing the real point following the established medical dogma.

This individual was not screened before, and probably would have not been screened at his doctor's office, it was a coincidental finding. He would have been patient zero after an epidemic of XDR TB cases.

Do we just say we were lucky this time? I would like to know how many of these "cases" are roaming our streets.

[FONT=Verdana, Helvetica, Arial]TB is a tough topic! Up until a few years ago 2005 I ran/was the primary attending on a service in a teaching nursing home .... affiliated with The Johns Hopkins Hospital.
Between the State of Md Health Dept regs. and the JHH gerontologists we two stepped Mantoux PPD’d every admission; young (50s and 60s in for rehab or post major medical disaster) as well as old.

There would be a case of a converter or a POS PPD every 6 to 9 months out of a census of 250 ....

The dilemma was always what to do. CXRs are often equivocal with old granuloma. Sputa are hard, you’re lucky if you get “red snappers” on the smear to get, and the Cx take a while.

We all had to get PPDs, but ... Docs tend to duck out. I had received BCG in the 70s and was POS once in the in the 80s and refused any more PPDs. I got away with that until the 90s and new regs and then tested negative as of the early 90s.
I then tested POS again and I had the x-rays etc. All NEG. After another POS reaction I told them no more and have gone with q.o.year to q. three years CXRs since.

We debated prophylactic antibiotics but and decided against that with the assumption the POS was still due to the BCG but, who really knows.

I also agree that the incidence is low in the general population but again I have picked up and treated about 6 new converters in 27 years in solo practice. I have seen two cases of laryngeal TB as inpatients ( not my patients thank goodness) contaminate a whole bunch of staff and (remember I am in Baltimore where we have S.E. Asian as well as Hispanic as well as Indian subcontinent immigrants as well as a large minority /HIV pos. IVDU population with a high incidence of STDs and other social dysfunction where TB breeds). I have seen an advanced case of Pott’s disease with a pathologically collapsed spine and active TB in the bone in an elderly lady as well as a case of renal TB.

With patients traveling to endemic areas (one new converter came back from a trip to Ceylon/Sri Lanka the year before) and more mobility you may need to rethink your population’s risks.

So you have to decide based on your patient population. I am a real big PPDer. I give patients a sheet with the increasing diameter circles and tell them if they cannot see or feel anything at 48 hours to just call us. If we do not hear, wee call or e-mail them.
If any doubt, or if more than 10mm they have to come in. Since I have switched to a smaller volume practice the phone calls and the follow up is a lot easier than before.
Still there are some folks who just slip through the cracks and I then I rely on the low incidence arguments to make myself feel better.

Hard topic, love to hear some other’s opinions and practices with respect to TB screening.[/FONT]

One article said there are 12 cases of XDR TB in the US. How crazy are you going to go about this? That’s a lot of CXR for 12 cases. And we don’t really know if he had symptoms. Maybe his sore ribs were the sx. He also said he didn’t think it would be a problem to fly as he wasn’t “coughing that much”.

We used to do routine screening of everyone and that turned out to be a waste of …I don’t know time, resources,. So now it’s just “high risk” but I guess we can all define our own “high risk”. It’s up to our discretion; you use yours.

Before antibiotics were available, TB was a great plague and source of human misery, poetic/philosophical inspiration. I can't recall the source, but I am under the impression that improvements in public health/hygiene, reduction in urban congestion were the reason TB infections/cases became rare.

I wish we had the specific details on this case, I can only assume that the XDR TB was diagnosed from a sputum culture, but the media is both alarming and trying to reassure us that everything is OK.

My real fear is that the end of our civilization will come with a whimper instead of a "Big Bang", MRSA, indolent intractable, untreatable TB and/or pandemic flu.

I have to come back to my personal level, what can I do to help my family and community?

It appears that we don't have adequate information to even prove that the incidence of XDR TB is less than 1%.

It is obvious that current guidelines are not being followed.

Another thing that worries me is that the young, clean-cut lawyer did not meet any screening criteria, and in the photo at the airport, his father-in-law is the only one not wearing a face mask.

Should the medical establishment change from the PPD test to the blood one? Would it be be cost effective?

I don't think we can learn anything from this high profile case.

I just read that the lawyer went to a meeting with CDC officials in Fulton County Georgia with a tape recorder and made them commit on tape an opinion about whether he was infectious. He got them to say that by policy he should not travel but that he was not a transmission risk. His family member is a TB expert and has access to multi drug resistant strains. Maybe that is his risk factor? Maybe he had contact with a TB infected client. He was quoted in the paper as saying that he flew to Canada on his return form Europe because he knew that he would be flagged on the TSA homeland security database. How did he know that? Is this a case of the privileged pushing the rules. Or is it a Booga booga show for us. Imagine if he was a Muslim or from the Mideast. He would be in Gitmo with his head in a bag by now.

If the recent pattern holds true, then we should expect some legislation to be proposed as a reaction to this that will restrict movement and violate civil rights.

It is nice to review the guidelines for our patient populations but this case is just plain weird.

QuantiFERON®-TB Gold Test

What is it?

The QuantiFERON®-TB Gold test (QFT-G) is a whole-blood test for use as an aid in diagnosing Mycobacterium tuberculosis infection, including latent tuberculosis infection (LTBI) and tuberculosis (TB) disease. This test was approved by the U.S. Food and Drug Administration (FDA) in 2005.
How does it work?

Blood samples are mixed with antigens (substances that can produce an immune response) and controls. For QFT-G, the antigens include mixtures of synthetic peptides representing two M. tuberculosis proteins, ESAT-6 and CFP-10. After incubation of the blood with antigens for 16 to 24 hours, the amount of interferon-gamma (IFN-gamma) is measured.
If the patient is infected with M. tuberculosis, their white blood cells will release IFN-gamma in response to contact with the TB antigens. The QFT-G results are based on the amount of IFN-gamma that is released in response to the antigens.
Clinical evaluation and additional tests (such as a chest radiograph, sputum smear, and culture) are needed to confirm the diagnosis of LTBI or TB disease.
What are the advantages?

• Requires a single patient visit to draw a blood sample.
• Results can be available within 24 hours.
• Does not boost responses measured by subsequent tests, which can happen with tuberculin skin tests (TST).
• Is not subject to reader bias that can occur with TST.
• Is not affected by prior BCG (bacille Calmette-Guérin) vaccination.

What are the disadvantages and limitations?

• Blood samples must be processed within 12 hours after collection while white blood cells are still viable.
• There are limited data on the use of QFT-G in children younger than 17 years of age, among persons recently exposed to M. tuberculosis, and in immunocompromised persons (e.g., impaired immune function caused by HIV infection or acquired immunodeficiency syndrome [AIDS], current treatment with immunosuppressive drugs, selected hematological disorders, specific malignancies, diabetes, silicosis, and chronic renal failure).
• Errors in collecting or transporting blood specimens or in running and interpreting the assay can decrease the accuracy of QFT-G.
• Limited data on the use of QFT-G to determine who is at risk for developing TB disease.

When should you use the test?

QFT-G can be used in all circumstances in which the tuberculin skin test (TST) is currently used, including contact investigations, evaluation of recent immigrants who have had BCG vaccination, and TB screening of health care workers and others undergoing serial evaluation for M. tuberculosis. However, caution should be used when testing certain populations because of limited data in the use of QFT-G.
Before the QFT-G is conducted, arrangements should be made with a qualified laboratory and courier service, if needed, to ensure prompt and proper processing of blood.
What are the steps in administering the test?

• Confirm arrangements for testing in a qualified laboratory and arrange for delivery of the blood sample in time for the laboratory to initiate testing within 12 hours of blood collection.
• Draw a sample of whole blood from patient into a tube with heparin anti-clotting agent, according to manufacturer’s instructions.
• Schedule an appointment for the patient to receive test results and, if then needed, medical evaluation and possible treatment for TB disease or LTBI.

How do you interpret test results?

Interpretation of QFT-G results is based on IFN-gamma concentrations in test samples. Each QFT-G result and its interpretation should be considered in conjunction with other epidemiological, historical, physical, and diagnostic findings.
A positive result suggests that M. tuberculosis infection is likely; a negative result suggests that infection is unlikely; and indeterminate result suggests QFT-G results cannot be interpreted as a result of low mitogen response or high background response.
A diagnosis of LTBI requires that TB disease be excluded by medical evaluation, which should include checking for signs and symptoms suggestive of TB disease, a chest radiograph, and, when indicated, examination of sputum or other clinical samples for the presence of M. tuberculosis.
Additional Information

Centers for Disease Control and Prevention. Guidelines for the investigation of contacts of persons with infectious tuberculosis and Guidelines for using the QuantiFERON®-TB Gold test for detecting Mycobacterium tuberculosis infection, United States. MMWR
2005; 54 (No. RR-15).
http://www.cdc.gov/mmwr/pdf/rr/rr5415.pdf (PDF)
Centers for Disease Control and Prevention. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005. MMWR 2005; 54 (No.RR-17).
http://www.cdc.gov/mmwr/pdf/rr/rr5417.pdf (PDF)

The quotes are from physicians in a discussion list.

 

[Deetee]

Skeptidoc - some advice....
Keep it simple, huh? If you want to evoke a response, try sticking to one or two salient questions or phrase them a bit tighter please. I tried composing a response, but apathy got to me in the end.
Try Tara'a blog for more info:
Here
Here

 

[skepticdoc]

Deetee, I am not looking for a "response" from any Pavlovian individual/subject.

I was hoping that Skeptigirl and others would share their expertise.

If your attention span is limited, just address the first 9 lines.

What do you do in your Gynecology practice?

Thanks for the link.