Criteria for the Processing of Dengue Samples at the CDC Dengue Branch, San Juan, Puerto Rico
The CDC Dengue Branch provides dengue testing free of charge to public health laboratories that need confirmatory testing. To obtain correct data on the spread of disease, adequately decide what laboratory tests to use, correctly interpret test results, and to assure that results get to the person who requested them, the following information is indispensable:
- Complete name, age, and sex of the patient
- Date of birth
- Pregnancy status
- Home address
- Date of onset of symptoms
- Date that sample was obtained
- Complete name and mailing address of the physician, laboratory, clinic, or hospital where results should be sent.
This information should be submitted on the CDC form 34-50 Cdc-pdf[PDF – 1 page], along with the collected samples.
Samples without the above-mentioned information, written with illegible handwriting, or with more than a month from date of sample collection to date of arrival at CDC, will not be analyzed.
In case of a severe dengue epidemic, CDC Dengue Branch will promptly analyze samples received with the minimum above-mentioned information. If number of specimens exceeds laboratory capacity, testing may be prioritized in the following order:
- Fatal cases
- Cases in intensive care
- Hospitalized cases (with thrombocytopenia, hemorrhage, shock, or hemoconcentration)
- All other cases.
Case Notification and Shipment of Samples of Suspected Dengue Cases
- Suspected dengue cases should be notified to Public Health Labs in the respective states and jurisdictions. Once there is a clinical diagnosis of suspected dengue, take a serum sample (see #4 and #5) and complete the CDC 34-50 specimen submission form Cdc-pdf[PDF – 1 page]. The information received on each case (especially the date of onset of symptoms and date of sample collection) is crucial to select and interpret laboratory results. Furthermore, a complete address makes it possible to identify the area where control measures should be implemented. Samples without the above-mentioned information, or with more than a month from date of collection to date of arrival at CDC, will not be analyzed.
- We recommend that you freeze serum immediately after separated and send in dry ice. The CDC Specimen Submission Form and the acute blood sample should reach CDC Dengue Branch as soon as possible. The acute sample can be sent immediately; there is no need to wait until the convalescent sample is collected.
- To diagnose dengue, the laboratory requires a serum sample collected during the acute period of the disease and a second sample collected from day 6 after the onset of symptoms. Informing the patient about the importance of coming back for a second sample, and giving an appointment for a specific day and hour, will increase the probability of obtaining the second sample. If the patient makes the first visit to the physician on or after day 6 after onset of the symptoms, that sample is sufficient. In that case, the patient does not need to return for collection of a second sample.
- Acute-phase samples (taken on or before day 6 after onset of symptoms), will be used mainly for molecular testing in order to detect viral RNA. Convalescent-phase samples (collected on or after day 6 after onset of symptoms) will be used mainly for detection of IgM anti-dengue antibodies by MAC-ELISA. Differential diagnosis for dengue and Zika, chikungunya and West Nile viruses is available; but these tests need to be requested according to clinical presentation. Samples taken on days 4 and 5 of illness are of low yield for isolation as well as serology. WHENEVER THERE IS A HOSPITALIZED SEVERE CASE, PLEASE INDICATE IT IN THE CDC SPECIMEN SUBMISSION FORM.
Case Notification and Shipment of Samples of Suspected Dengue Cases Type of sample Interval Since the Onset of Symptoms Type of Analysis Acute Serum 0-6 days of illness NAT and MAC-ELISA Convalescent Serum 7 or more days of illness MAC-ELISA
- CDC will report results to the submitting state lab. In cases with negative results on the acute sample, we will instruct the submitter to collect and provide a convalescent-phase sample before concluding in the overall diagnosis of the patient.
- Results will be reported only to the laboratory who sent the sample.
Dengue Branch, CDC
1324 Cañada St.
San Juan, PR 00920-3860
Tel. (787) 706-2399
Fax (787) 706-2496