Download Syzygy Nov-Dec 2010 - Sullivan Nicolaides Pathology

November/December 2010
syzygy
Laboratory Diagnosis of Dengue Infections
SNP adds early diagnosis marker
NS1 to dengue test panel
Dengue cases worldwide continue to climb. It is the most common
cause of fever in returned travellers. As well, outbreaks occur in the
north of our state. The inability of serologic methods to reliably diagnose
acute infections has been a serious impediment to quick identification
of cases, and thus effective clinical case management, and the ability to
intervene and implement outbreak control strategies.
If the blood sample has been collected within the first five days of
illness, dengue IgM may be negative. PCR has significantly improved
this, although PCR is not always immediately available outside reference
laboratories. In addition, serological diagnosis poses a number of
pitfalls including cross-reactivity among other flaviviruses.* 'Original
antigenic sin'** can complicate specific diagnosis of secondary flavivirus
infections. IgM may be low or absent in secondary infection, and IgM
may persist for 3 months or more following acute primary infection
making accurate serological timing of infection difficult (Figure 1).
To overcome these problems, the detection of a non-structural protein
(NS1) present in the serum of infected individuals has been developed.
The protein appears as early as the first day of the fever and is not
inhibited by the development of dengue IgM antibodies. It peaks at
around days 3-5 and subsides around day 9.
The immune response to dengue virus infection can be considered in
the context of primary versus secondary dengue infections (Figure 1).
A primary infection describes the first dengue virus infection
experienced by an individual.
• NS1 antigen is produced from day 1 up to day 9 after onset of fever.
• Detectable levels of IgM antibody will be produced by day 5 of
infection, sometimes as early as day 3. IgM levels peak in 2 weeks,
usually becoming undetectable at 2 to 3 months.
• Low levels of IgG are detected in the early convalescent phase, and
not during the acute phase.
A secondary infection is a subsequent infection with a dengue serotype
to which that person has not previously been exposed. A secondary
immune response is generated. Such a response may also be triggered if a
person has previously been exposed to a flavivirus (either through infection
or vaccination) that is not dengue.
• NS1 antigen is produced from day 1 up to day 9 after onset of fever.
• The IgM response is more varied and often preceded by IgG. A
minority of patients will show low or no detectable IgM levels.
• High levels of IgG are detectable during the acute phase and reach
levels above those found in primary or past infection. IgG may be
detectable by day 3 of symptoms, and is generally detectable day 5-6.
Levels persist for 30-40 days, then decline to levels found in primary
or past infection.
*Flaviviruses are arthropod-borne viruses. Those endemic in Australia and of clinical
importance include dengue, the encephalitic group (Murray Valley encephalitis {MVE}
and Kunjin) and infrequently the non-encephalitic group (Kokobera and Stratford).
International travellers may encounter flaviviruses including dengue, Japanese B
encephalitis (JE), West Nile virus (WNV), yellow fever and tickborne encephalitis.
**'Original antigenic sin' is a secondary immune response which occurs when
B lymphocytes are exposed to closely related but not identical antigens.
The antibodies formed react more strongly with the antigen that elicited the
primary response.
For more information please contact Microbiologist on (07) 3377 8534
or email: [email protected]
Figure 1
Aedes aegyptit is the vector for transmission of dengue infection.
Photograph courtesy of Stephen Doggett (University of Sydney)
patient care first
Screening for Group B Streptococcus
in Pregnancy
The Safe and Effective Management
of Warfarin
Warfarin Care’s mission is to provide safe and effective management
of patients on warfarin. We recognise that the referring doctor has
primary clinical responsibility for the patient at all times and that we
work in a collaborative arrangement to deliver high quality patient
care with the best patient outcomes.
As part of our proven effective strategies for managing Warfarin
dosing in as safe a manner as possible, it is important that patients on
Warfarin have a Full Blood Count and Liver Function Test done at sixmonthly intervals. This provides critical information on all patients for
the doctors who perform the dosing and is particularly helpful when
the patient‘s INR fluctuates or dosing requirements change.
At your next consultation with the patient, and if your
patient has not had these tests in the past six months,
could you please provide them with a request for
FBC and E/LFT. These tests can then be performed in
conjunction with your patient's regular INR test.
Along the same lines it is important that when SNP Warfarin
Care manages your patient’s OAC therapy that all of the patient’s
pathology should be performed with SNP. This allows the Warfarin
Care doctors when determining the next Warfarin dose to access
these results and be informed by them to provide the best dosing
advice and patient outcome.
Changes to any medication (including many types of prescribed,
herbal and over-the-counter substances) are the most common causes
of unexpected changes in the INR. As part of good management, the
patient’s requirement for ongoing medication and their recent INR and
other results should be reviewed at each visit to their doctor.
The importance of good communication between all parties – patient,
primary treating doctor and warfarin care doctor – cannot be stressed
enough; your ongoing participation and interaction is essential in the
safe delivery of this service. For this reason, we can accept patients
onto the programme only if all these requirements are met.
For more information please contact Dr Huong Phan FRACP, FRCPA
on (07) 3377 8521 or email: [email protected]
Group B Streptococcus (GBS) is a leading cause of early onset neonatal
sepsis. Approximately 15-25% of women will be asymptomatic carriers
of Group B Streptococcus of which, if left untreated one in 200 will have
neonates that will develop neonatal sepsis.
Guidelines for prevention of early onset neonatal GBS have recommended
either a risk-based or screening approach to identify pregnant women for
intrapartum antibiotic prophylaxis.
For the screening approach, GBS carriage is best predicted by prenatal
screening at 35-37 weeks gestation with a combined low vaginal and
anorectal swab placed into a selective enrichment broth medium. Culture
results are less predictive of status at term if performed at earlier gestations.
This swab can be clinician collected or patient self-collected. Patient
collection notes can be located at http://www.ranzcog.edu.au/publications/
statements/GBS%20SWAB%20SHEET3.pdf
What to REQUEST – Group B Strep Screen
clinical information – Pregnant/Gestation
Specimen type – Combined anovaginal swab (can be self-collected)
Swab type – Red top swab suitable for bacterial culture
Reference: http://www.ranzcog.edu.au/publications/statements/C-obs19.pdf
For more information please contact Microbiologist on (07) 3377 8534
or email: [email protected]
PLAN NOW FOR WARFARIN CARE
ENROLMENTS OVER CHRISTMAS 2010
Warfarin Care will be closed for new enrolments from 4 pm Wednesday 8
December 2010 and will re-open 8 am Tuesday 4 January 2011. This closure
is necessary to allow the safe transfer of patients onto our program.
For more information please contact our Warfarin Care team on
(07) 3377 8578, or visit the 'Doctor Services' area at www.snp.com.au.
Check our website www.snp.com.au closer to Christmas for an update on
collection centre hours over the festive season.
collection centre updates
Brisbane Now Open
REGIONAL Now Open
Bellbowrie
8 Birkin Road
Phone (07) 3432 9559
Mackay
Oasis Plaza
118 Sams Road
Phone (07) 4942 5747
West End
73-77 Russell Street
Phone (07) 3846 6413
Geebung
328 Newman Road
Phone (07) 3216 2014
Burpengary
33 Progress Road
Phone (07) 3377 8747
Brisbane OPENING SOON
Test Tip
Faeces for Reducing substances
Re-collections can be avoided by ensuring that samples for reducing
substances are FROZEN immediately after collection by the patient and
remain FROZEN during transportation to our laboratory.
When samples are not frozen, the bacteria in the faeces consume the
carbohydrates and give false negative results.
Calamvale
2605 Beaudesert Road
Phone (07) 3377 8747
Mudgeeraba
67 Railway Street (rear of building)
Phone (07) 5559 1092
Peregian
Shop 8 'Marguesas'
David Low Way
Phone (07) 5459 1400
REGIONAL relocated
Noosaville (next door to Noosa
Radiology)
Shop 3.07a, 90 Goodchap Street
Phone (07) 5474 3506
visit www.snp.com.au
for pathology collection centre opening times
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