Meaningless Rickettsia results?

Gondwanaland

Gondwanaland

Senior Member
Messages
5,100
Just got my husband's Rickettsia results:

RICKETSIA RICKETTSII IGG antibodies
Indirect immunofluorescence (blood)
<1:40 (negative= <1:64)

RICKETSIA RICKETTSII IGM antibodies
Indirect immunofluorescence (blood)
<1:10 (negative= <1:64)

I find it funny that there is a specific number above which one can be considered ill (>1:64)

Any input on these results anyone?
 
Jonathan Edwards

Jonathan Edwards

"Gibberish"
Messages
5,256
These are rather odd figures. They are dilutions and the figure given will be the highest dilution at which an immunfluorescent signal can be detected. What is odd is that dilutions go in doublings, so they are often
1:10, 1:20, 1:40. 1:80, 1:160 or
1:4, 1:8, 1:16, 1:32, 1:64

So having results of 1:10 or 1:40 with a reference cut off of 1:64 does not make much sense.

I cannot say how the reference cut off is arrived at but would expect it to indicate the level below which the great majority of normal controls are found or some statistically calculated level that best distinguishes known cases from controls. It would not be intended to be interpreted as 'ill or not' on its own I think - it would contribute to a physician's evaluation of the probability of infection.
 
O

Oredogg

Messages
53
Location
Oregon
I'm with @Jonathan Edwards the reference range does not make sense with the patient result. The patient testing should be done in the same manner as the reference interval. I'd raise this issue to the lab, since you are paying for this test, and have them explain and/or repeat the test with appropriate controls. I am a pathologist and former lab director, so this is an area I have some experience with.
 
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