Are negatives REALLY negative?

[sara.smiles]

Indonesian officials are taking a bit of delight in reporting all these hospitalized cases (hi fever, cough, shortness of breath) are having their bloodwork come back as negative for H5N1. Am I the only one who's not believing it? Or could this really be seasonal influenza?

I know that these all produce false negatives:
Sampling too early
Sampling too late
Sampling the wrong body fluid for the stage of the illness
Treatment with Tamiflu

Considering that the US sent all our reserves of Tamiflu "somewhere" and mysteriously, now Indonesia has enough Tamiflu to blanket outbreak areas, it's apparent that the Tamiflu is masking the real magnitude of the problem.

Is WHO taking all this with a grain of salt? It's obvious that Indonesia is on the verge of exploding, if this is in fact H5N1. Now that Vietnam has started reporting new cases again, the early warning system in me is ringing loudly!!

Thoughts??

 

[Mingus]

Re: Are negatives REALLY negative?

From http://www.cdc.gov/flu/professionals/labdiagnosis.htm

Lab Diagnosis

(...)
Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, polymerase chain reaction (PCR), and immunofluorescence assays. Sensitivity and specificity of any test for influenza might vary by the laboratory that performs the test, the type of test used, and the type of specimen tested.
(...)
Appropriate samples for influenza testing can include a nasopharyngeal or throat swab, nasal wash, or nasal aspirates, depending on which type of test is used. (See table.) Samples should be collected within the first 4 days of illness
(...)

Talking about commercial fast tests ( not thoses made in labs )
(...)
. Thus, as many as 30% of samples that would be positive for influenza by viral culture may give a negative rapid test result. And, some rapid test results may indicate influenza when a person is not infected with influenza.

<TABLE class=table cellSpacing=0 cellPadding=3 align=center summary="Influenza Diagnostic Table"><CAPTION>http://www.flutrackers.com/forum/Influenza Diagnostic Table

</CAPTION><TBODY><TR><TH>

Procedure​

</TH><TH>

Influenza Types Detected​

</TH><TH>

Acceptable Specimens​

</TH><TH>

Time for Results​

</TH><TH>

Rapid result available​

</TH></TR><TR vAlign=top><TD>Viral culture </TD><TD>

A and B​

</TD><TD>NP swab<SUP> 2 </SUP>, throat swab, nasal wash, bronchial wash, nasal aspirate, sputum </TD><TD>

5-10
days<SUP> 3</SUP>​

</TD><TD>

No​

</TD></TR><TR vAlign=top><TD>Immunofluorescence DFA Antibody Staining </TD><TD>

A and B​

</TD><TD>NP swab<SUP> 2 </SUP>, nasal wash, bronchial wash, nasal aspirate, sputum </TD><TD>

2-4 hours​

</TD><TD>

No​

</TD></TR><TR vAlign=top><TD>RT-PCR <SUP>5</SUP> </TD><TD>

A and B​

</TD><TD>NP swab <SUP>2 </SUP>, throat swab, nasal wash, bronchial wash, nasal aspirate, sputum </TD><TD>

1-2 days​

</TD><TD>

No​

</TD></TR><TR vAlign=top><TD>Serology </TD><TD>

A and B​

</TD><TD>paired acute and convalescent serum samples <SUP>6</SUP> </TD><TD>

>2 weeks​

</TD><TD>

No​

</TD></TR><TR vAlign=top><TD>Enzyme Immuno Assay
(EIA) </TD><TD>

A and B​

</TD><TD>NP swab<SUP> 2 </SUP>, throat swab, nasal wash, bronchial wash </TD><TD>

2 hours​

</TD><TD>

No​

</TD></TR></TBODY></TABLE>

 

[LMonty]

Re: Are negatives REALLY negative?

Appropriate samples for influenza testing can include a nasopharyngeal or throat swab, nasal wash, or nasal aspirates, depending on which type of test is used. (See table.) Samples should be collected within the first 4 days of illness

I'd bet good money that most providers do not know the time limit on this. I see it being done on human flu infections, as far as a week after symptom break. I didnt know it either until I learned it on the flu boards.

Does anyone know how long the serology stays positive for?

 

[prepdeb]

Re: Are negatives REALLY negative?

Indonesia is really a source of concern. The "official" numbers don't seem to change much despite continual reports of people entering hospitals with classic symptoms

Most end up testing negative, which no doubt has much to do the the mass distribution of Tamiflu in outbreak areas. Many die without ever being tested and the ones who test negative leave the hospital and return to the community.

What are they thinking? I'm a dummy when it comes to medical and scientific areas, but even I can see what a mess it is and how current methods can only enable the virus.

I continue to prep although most around me no longer even think of a possible pandemic. To them, that was yesterdays' news and it didn't happen so there's no need to be concerned.

 

[sharon sanders]

Re: Are negatives REALLY negative?

"Many die without ever being tested and the ones who test negative leave the hospital and return to the community."

While there is some lack of clarity on the exact case numbers, many are not dying. These deaths would be noticed. There are many international media there in addition to international organizations.