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Antibody titer
Make it clearer
When a lab looks for antibodies, it often cannot count them one by one. What it does instead is more clever: it waters the sample down with saline, a little at a time, and watches how far it can go before the reaction disappears. That is the dilution.
The titer is exactly the last dilution at which the reaction is still visible. That is why it is written as a ratio, 1:16: it means the sample held up to being watered down sixteen times and still showed a reaction. In other tests the result is reported in units instead of a ratio; a health care worker who has completed the hepatitis B series and has 10 mIU/mL of anti-HBs is considered immune.
Two cautions. The hepatitis B titer does not hold steady: it falls over the years. And the number that matters is not the same from one test to another: on the RPR, the syphilis test, a titer of 1:32 or higher points to a higher risk of neurosyphilis, a threshold that cannot be carried over to another test.
In brief
A titer is not an amount: it is how far the sample can be diluted before the signal is lost.
The more you can dilute it without losing the reaction, the higher the titer.
It is the highest dilution at which the reaction is still visible: 1:16, for example.
After the hepatitis B series, a health care worker with 10 mIU/mL of anti-HBs is considered immune.
That titer falls over the years; each test sets its own threshold, and RPR flags risk of neurosyphilis starting at 1:32.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingRapid Plasma Reagin, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingHepatitis B Vaccine, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated