Pertussis Diagnosis and Testing

What You Need to Know

By Vincent Iannelli, M.D., About.com Guide

Updated February 09, 2011

About.com Health's Disease and Condition content is reviewed by the Medical Review Board

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Pertussis Diagnosis and Testing

Although the initial diagnosis of pertussis is usually based on the characteristic symptoms, testing is available. This includes a culture of nasal secretions, however the results can take up to 10-14 days to come back, after which time the person has likely passed the infection to many other people.

A quicker test, but which may not be as accurate, is a DFA (direct immunoflourescent assay) of nasal secretions. Although Pediatricians will likely not be able to do this test in their office, it is a test that they can arrange to have done through a local lab or they can have it sent off.

An additional test, the PCR or polymerase chain reaction test, is both faster and more accurate than other testing, but may not be widely available yet.

Children with pertussis may also have a lot of lymphocytes (lymphocytosis) on a complete blood count.

To help with reporting and tracking of cases of pertussis, the following definitions were developed by the CDC:

A clinical case is defined as an acute cough illness lasting >14 days in a person with at least one pertussis-associated symptom (i.e., paroxysmal cough, post-tussive vomiting, or inspiratory whoop) or >14 days of cough in a person in an outbreak setting.
A confirmed case is defined as a cough illness of any duration in a person with isolation of Bordetella pertussis, or a case that meets the clinical case definition and is confirmed by polymerase chain reaction (PCR) or by epidemiologic linkage to a laboratory-confirmed case.
A probable case meets the clinical case definition but is not laboratory confirmed or epidemiologically linked to a laboratory-confirmed case.

If your child meets the definition of a clinical case and has a chronic cough and either a paroxysmal cough, post-tussive vomiting, and/or an inspiratory whoop, or if he has a chronic cough that just isn't getting better, you should ask your Pediatrician about pertussis, especially if your child has been around a teen or adult with a cough. Other warning signs to look for include a cough that is interfering with your child's ability to eat, drink or breath, especially if he has tested negative for other common childhood infections, such as RSV.

You should also ask about pertussis if you have a teen with a chronic cough, or if you yourself have a cough that is lingering, which may be misdiagnosed as bronchitis or a sinus infection.

Early recognition and treatment of a case of pertussis is important and may help the bacteria from being spread to others, especially young children who are most at risk.

The Future of Pertussis

Since pertussis mostly affects teens whose immunity to pertussis from their childhood vaccines has worn off, giving a booster dose of pertussis, like we do for tetanus at age 11-12 years, makes sense. Why isn't this done? The main reason this wasn't done in the past, is that a pertussis vaccine was not approved for children over age 7 years until just recently. Fortunately, a vaccine for older children, teens, and adults, is now available and this Tdap vaccine will hopefully prevent more pertussis infections.

^Sources

¹Lebel MH - Pediatr Infect Dis J - 01-Dec-2001; 20(12): 1149-54 Efficacy and safety of clarithromycin versus erythromycin for the treatment of pertussis: a prospective, randomized, single blind trial. ²Recommended Antimicrobial Agents for the Treatment and Postexposure Prophylaxis of Pertussis. 2005 CDC Guidelines. MMWR. December 9, 2005 / 54(RR14);1-16