Quick answer: A Widal result such as "O 1/160" means antibodies to typhoid bacteria were still detected after your blood was diluted 160 times. A higher titre can support a diagnosis of typhoid, but a single Widal result can't prove it. Many people in Nigeria carry antibodies from past infections, so the doctor reads the result together with your symptoms.
What the numbers mean
The Widal test mixes your blood serum with typhoid antigens at increasing dilutions: 1/20, 1/40, 1/80, 1/160, 1/320 and so on. The result is the highest dilution that still reacts. The report usually lists:
- O antigen (TO): antibodies that rise early in infection
- H antigen (TH): antibodies that can stay high for months or years after past infection or vaccination
- AH and BH: antibodies to paratyphoid, a related infection
Why a positive Widal can mislead
- Past typhoid, typhoid vaccination and repeated exposure leave antibodies behind, so many healthy people in Lagos have some titre.
- Malaria and other infections can cause false positive reactions.
- Early in typhoid, antibodies may not have risen yet, so the test can be negative.
As a rough guide, an O titre of 1/160 or more in someone with typical symptoms makes typhoid more likely. A rise of four times or more between two samples taken about a week apart is stronger evidence. A single low titre, such as 1/40 or 1/80, without symptoms usually means nothing.
Which tests confirm typhoid?
A blood culture, ideally in the first week of fever, is the most reliable test, and stool culture can help later in the illness. Our doctor may arrange these if typhoid seems likely.
Symptoms that point to typhoid
- Fever that climbs over several days and doesn't settle
- Headache, weakness and loss of appetite
- Stomach pain, constipation or diarrhoea
Taking antibiotics because of a Widal result alone is a common cause of antibiotic resistance in Nigeria. Let a doctor decide. Read more: malaria vs typhoid.
When to go to hospital
Severe stomach pain, a swollen stomach, blood in stool, confusion or very high fever that won't come down need a hospital today. Mascot Healthcare doesn't handle emergencies.
Get tested in Akoka
The Widal test is walk-in at Mascot Healthcare, 52 Sholanke Street, off Chemist Junction, Akoka, Lagos, Monday to Saturday, 9 AM to 5 PM. See the malaria and typhoid test, or book a consultation for typhoid treatment. Prices are on our price list.
This article is general information, not a diagnosis.