Transcript collection and transport of virological specimens.

COLLECTION AND TRANSPORT OF VIROLOGICAL
SPECIMENS.
•In the investigation of viral infections, reliable laboratory results
can only be obtained if the specimens are collected, preserved
and transported correctly to the Virology laboratory.
•When to collect virological specimens?
•Specimen for detection of viruses should be collected as soon
as possible after the appearance of the symptoms that is when
the concentration of the virus is at its highest.
•Blood for antibody testing should be collected as early in the
disease as possible and also 5- 10 days later.
•Two serum specimens (paired sera) are necessary to detect a
rise in the titre of the Ab. A four fold rise in titre between paired
sera establishes a positive result.
Collection of virological specimens:
•The type of the specimen required will depend on:
1. The viral infection suspected.
2. The laboratory technique to be used.
•District and local laboratories must obtain information about
the collection of specimen from their Virology Reference
Laboratory.
The following information is intended only as a general guide:
•Faeces:
1. Place about 4-8 g of faeces (small spoon) in a clean, dry,
leak-proof container (not a waxed carton).
2. Deliver to the laboratory as soon as possible.
3. If there is likely to be a delay to more than few hours in the
specimens reaching the laboratory, suspend about one gram of
faeces in 9 ml of phosphate buffered saline. If possible
centrifuge at 2000g for 15 minutes, and then transfer the
supernatant fluid to a clean leak- proof container.
4. Label and keep at -20 OC.
5. Send to the virology laboratory in a cold box.
6. If a faeces sample can not be obtained, rectal swab
should be collected and transported in buffered saline.
7. The isolation of viruses from rectal swab however, is less
satisfactory than from faeces.
8. Faeces specimens are required to diagnose viral
gastroenteritis specially that caused by rotaviruses, and to
investigate poliomyelitis and other diseases caused by
enteroviruses.
2. Nasopharyngeal secretions:
A.Collect a specimen by passing a sterile cotton wool swab,
attached to a pent piece of thin wire, through the floor of the
nasal cavity as far as the nasopharynx.
B. After few seconds, slowly withdraw the swab and immerse the
swab in a container of sterile VTM, cutting off swab wire to allow
the bottle cap to be replaced tightly.
C. A specimen of nasopharyngeal secretion can also be
obtained by using a sterile mucus extractor.
D. Respiratory viruses can also be recovered from a throat swab
preserved in VTM but a pernasal swab is usually easier to obtain
and has been found very satisfactory for the isolation of
influenza viruses, measles virus, and respiratory syncytial
viruses.
E. A throat swab is unsuitable if the specimen is to be
tested by a fluorescence antibody technique.
F. Nasopharyngeal specimens are required to diagnose
respiratory syncytial virus infection, and when
necessary to investigate infections caused by influenza
and parainfluenza viruses, measles, rubella virus,
adenoviruses, and enteroviruses
3. Cerebrospinal fluid:
•Collect 0.5- 1.0 ml of fluid in a dry, sterile, leak-proof container. Refrigerated
immediately at 4 OC.
•Transport in an insolated cold box.
•Cerebrospinal fluid is required to investigate some arbovirus infections.
When meninges are infected, the CSF will contain lymphocytes and the CSF
total protein will be raised.
4. Skin and ulcer specimens:
•Collect skin scrapings in a dry sterile container.
•Refrigerate immediately at 4OC, and then transport in a cold box.
•If measles or rubella is suspected, the virus is more likely to be isolated from
a per nasal swab.
•Skin specimens are required to investigate infections caused by herpes
simplex viruses, rabies viruses….
5. Blood for serological tests:
•Two serum specimens are required to diagnose an infection
serologically.
•Collect the sample within 5 days of the onset of the symptoms,
and the second sample 5-10 days later.
•Collect 5-10 ml of venous blood in a dry sterile, screw-cup glass
tube or bottle.
•A single sample is required for investigating newborn infant with
congenital defects, determining immunity to rubella or other
viruses…
•A single serum sample is required when testing for hepatitis B
surface Antigen (HBsAg) and HIV-1 and HIV-2.
•After the blood collected, collect in leak-prove container,
refrigerate at 4C until transport it in ice box to the virology lab.
6. Anticogulated blood for culture:
•Collect 7-10 ml of blood into a sterile tube or bottle which
contains heparin, gently mix the blood with the anticoagulant.
•Viruses which can be cultured from blood include dengue
viruses and some arboviruses.
7. Specimens such as urine and sputum are generally
unsuitable for viruses' isolation.
All samples which may contain dangerous and highly infectious
viruses must be labeled HIGH RISK with a red marker pen, and
handled with great care.
•Labeling of specimens:
This should be including:
•Patient's name and number.
•Hospital or health centre.
•Type of specimen.
•Date and time of collection.
•Container tops should be sealed with adhesive tape
to prevent slacking during transit.
•Information to accompany specimens:
A request form should include the fallowing information:
1. Name, place, age, number of the patient, and details
of any recent travel.
2. Type of specimen, if two, mention as the first of
second.
3. Investigation required.
4. Full clinical information: nature duration, and severity
of disease.
5. Details about immunization and antimicrobial therapy.
6. Name and address of the hospital or health centre.
*IF THE SAMPLE IS HIGH RISK, THE SAME SENTENSE SHOULD BE
WRITTEN IN THE FORM BY THE RED COLOR PEN.
•The form should not be wrapped around the specimen container but placed
separate it, inside the outer container where it will be found immediately
when the package is opened.
Transporting of specimens to the Virology laboratory:
•Viruses are unable to survive temperature over 50 C, freezing or
fluctuatings in temperature.
•Viruses can also be damaged be light, drying, change in pH, and bacterial
enzymes.
•The usage of VTM will prevent specimens from drying out and help to
preserve viral activity.
•All virological specimens should be transported in ice box with the warning
label.