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Pertussis Facts | Physician Information | Other Resources

Diagnostic and Treatment Criteria

Updated September 11, 2002

Pertussis should be considered when evaluating any patient with an acute cough illness characterized by one or more of the following symptoms: prolonged cough, cough with paroxysms, whoop, or post-tussive gagging/vomiting. Infants may present with apnea and/or cyanosis. An increased white blood cell count with lymphocytosis is a characteristic but nonspecific finding. Adults, teens, and vaccinated children often have mild symptoms that mimic bronchitis or asthma.

Pertussis immunity is not absolute (100%) and may not prevent infection. Older children and adults with mild illness can transmit the infection and are often the source of illness in infants. Therefore, early recognition and treatment of pertussis in contacts of young infants and prophylaxis of their household members is especially important.

Laboratory tests should be used in conjunction with clinical symptoms for diagnosis and can be used to confirm but not rule out pertussis. The organism is more likely to be found early in the coughing phase. After 3–4 weeks of cough the organism may have cleared the nasopharyngeal area, although unvaccinated infants may remain culture-positive for more than six weeks.

Treatment of suspects and contacts may include either erythromycin or trimethoprim/sulfamethoxazole administered for 14 days. If these drugs are not tolerated, clarithromycin or azithromycin can be substituted. Initiating treatment more than 3 weeks after cough onset has limited benefit to the patient or their contacts except for high-risk patients. Symptomatic women late in pregnancy and exposed infants should be treated within 6 weeks of onset or exposure. Symptomatic children and/or adults may return to school or work only after completing the first 5 days of medication.

If pertussis is clinically suspected:

• Report immediately to your local health authority at (800) 705-8868 or (800) 252-9152. This will initiate an epidemiological investigation and assure that appropriate control measures are initiated in all settings.
• Begin chemoprophylaxis of patient and all household and close contacts regardless of age or vaccination status.
• Submit specimens for laboratory confirmation. The preferred laboratory test for confirmation of pertussis is isolation of Bordatella pertussis by culture. Polymerase chain reaction (PCR) testing is also available in some labs, and is considered confirmatory when consistent with a clinical diagnosis.
• Review immunization records for children less than 7 years of age. Children in this age group who have not completed the DTaP four dose primary series should complete the series with minimal intervals. Those who have completed the primary series should be given a booster dose if their last dose of DTaP was given more than 3 years ago.

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Pertussis Tests

The tests of choice for confirmation of pertussis are isolation from culture or detection of unique DNA patterns by PCR. DFA lacks both sensitivity and specificity and therefore is not considered confirmatory. Antibody tests for IgG and IgA antibodies to fimbria, pertussis toxin, and filamentous haemagglutinin may provide supportive evidence of infection after several weeks of illness.

B. pertussis is more likely to be found during the early stage of infection. By the time a clinical diagnosis is made the organism may have cleared the nasopharyngeal area especially if any antibiotic therapy has been initiated. Negative tests results should not be used to rule out pertussis. In practice, the diagnosis and treatment should be based on symptoms and the course of illness.

Test Availability

Pertussis tests are available commercially, at most hospital labs, and at the Texas Department of Health (TDH). If needed, test kits can be ordered when calling your local health department at (800) 705-8868 to report suspected cases of pertussis, or can be ordered from TDH by calling (512) 458-7661. Kits can be shipped overnight upon request.

Specimen Collection

Either a nasopharyngeal (NP) swab or an NP aspirate is the specimen of choice for culture, polymerase chain reaction (PCR), or direct fluorescent antibody (DFA) tests. Throat swabs and anterior nasal swabs are not acceptable for the evaluation of pertussis. Because B. pertussis is fastidious and its isolation in culture is easily obscured by growth of other nasopharyngeal organisms, optimal sampling and handling of the specimen will improve the rate of recovery.

Nasopharyngeal Swab

• Immobilize the patient's head.
• Gently insert either a thin-wire calcium alginate or Dacron swab into a nostril until the posterior nares is reached.
• Leave the swab in place for up to 10 seconds. This procedure may induce coughing and tearing.
• If resistance is encountered during insertion of the swab, remove it and attempt insertion on the opposite nostril.
• Remove the swab slowly.

Appropriate positioning of a nasopharyngeal swab

Nasopharyngeal Aspirate

• Immobilize the patient's head.
• Gently insert a small tube connected to a mucus trap into the nostril back to the posterior pharynx. Insertion may induce coughing and tearing.
• Aspirate secretions while the tube is in that position and as it is slowly withdrawn to the middle of the nasal cavity.
• Material in the mucus trap and any material flushed from the tube can be used to inoculate culture media for isolation of B. pertussis.
• The specimen may be split for use on 2 or more tests such as culture, PCR, or DFA.

Pertussis Culture

• Use Regan-Lowe (RL) transport media. Roll the swab across the slanted surface of an RL transport slant, and then place the swab into an RL transport deep, pushing swab down into the medium. Cut off the shaft of the swab at the top of the tube and replace the cap.
• Label the slant and deep tubes with the patient's name and date of birth or social security number.
• If there is a delay of more than two (2) hours between collection and shipment, refrigerate specimens.
• Ship specimens via overnight delivery on cold packs or wet ice within 48 hours of collection.

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Treatment & Prophylaxis

¹ Drug of choice

² Recommended as an alternative antibiotic treatment form patients who cannot tolerate erythromycin. TMP/SMZ should not be given to pregnant women near term, nursing mothers, or infants <2 mos.

³ Judged likely to be effective by the American Academy of Pediatrics based on in vitro susceptibility studies. Also recommended as an alternative antibiotic treatment for patients who cannot tolerate erythromycin.

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