NICE on Lyme disease this month – just in time for the weather to pick up and the tics to start biting. Also a reminder on the risk factors for SIDS, what to do in a terrorist attack, how to manage a child with a non-blanching rash and a discussion on the use of the antistreptolysin O titre. Do leave comments below:
A patient was referred to me in the paediatric cardiology clinic because of a risk that he may have had missed Kawasaki’s disease a couple of weeks earlier and was therefore at risk of having coronary artery aneurysms. The referring doctor had carried out an antistreptolysin O titer (ASOT) in case the symptoms of a red, sore mouth, rash and later peeling fingers had been secondary to a streptococcal infection rather than KD. The result came back as 400units/ml (normal is < 200units/ml). The child was very well when I saw him and had a normal echocardiogram. What should I do with the elevated ASOT result?
I needed a quick text box as a gap filler for the April edition of the Paediatric Pearls newsletter and thought ASOT results would be a suitable topic but, when I sat down to write it, I opened up a can of worms. No one really knows what to do with high ASOTs in a well child. In fact, authors can’t even agree on whether 400 is elevated in a young person.
My reading list is at the foot of this article. Salient points from these sources are summarised below.
- The ASOT is ordered primarily to determine whether a previous group A Streptococcus infection has caused a poststreptococcal complication, such as rheumatic fever or glomerulonephritis. So the start point should be on-going clinical symptoms of strep infection or the effect of a recent infection. If used in this way, it can be a useful pointer to a causative organism and will guide management. Rheumatic fever is treated with long term antibiotics. The ASO test does not predict whether complications will occur following a strep infection, nor does it predict the type or severity of the disease. If symptoms of rheumatic fever or glomerulonephritis are present, an elevated ASO level may be used to help confirm the diagnosis.
- ASO antibodies are produced a week to a month after an initial strep infection. The amount of ASO antibody (titer) peaks at 3 to 5 weeks after the illness and then tapers off but may remain detectable for several months after the strep infection has resolved.
- A negative ASO or ASO that is present at very low titers means the person tested most likely has not had a recent strep infection. This is especially true if a sample taken 10 to 14 days later is also negative (low titer of antibody) and if an anti-DNase B test is also negative (low titer of antibody). A small percentage of people with a complication related to a strep infection will not have an elevated ASO. This is especially true with glomerulonephritis that may develop after a skin strep infection.
- An elevated titer of antibody (positive ASO) or an ASO titer that is rising means that it is likely that the person tested has had a recent strep infection. ASO titers that are initially high and then decline suggest that an infection has occurred and may be resolving.
My conclusion at the end of reading about ASOT and the management of streptococcal infections and complications is that I should only do the ASOT if the child is symptomatic. If I think they have rheumatic fever, I should treat with antibiotics for a long time (up to 10 years in some cases). If they do not satisfy the Jones criteria for rheumatic fever and indeed are well now, I do not need to blindly treat an elevated ASOT but it may be prudent to repeat the test a couple of weeks later to ensure it is dropping.
Very good summary article on rheumatic fever: https://patient.info/doctor/rheumatic-fever-pro
Why treat sore throats at all? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1949249/
Cochrane on short term antibiotics: https://www.ncbi.nlm.nih.gov/pubmed/22895944
In children with suspected malaria do we need three negative blood films to exclude a diagnosis of Malaria?
– with thanks to Dr Tom Waterfield for summarising his recent article (5) below for Paediatric Pearls
There are over 300 new cases of imported paediatric malaria in the UK each year and cases of imported malaria here have been increasing over the last 20 years (1). Malaria in children is particularly difficult to diagnose because the initial presenting features are subtler than in adults. Children may appear quite well initially with a fever and no focus but; they are at risk of a rapid deterioration and are more likely to develop severe malaria.
The “gold standard” for ruling out the diagnosis of malaria if clinically suspected is three negative thin and thick blood films (2). This approach however, relies on serial phlebotomy and the availability of adequately trained staff. Furthermore, during out-of-hours periods the time and resources required are likely to result in delays in obtaining results especially if trained staff have to come in from home. There are now a range of Rapid Diagnostic Tests (RDTs) that are highly specific and sensitive for malaria. So are three films really required when we have RDTs?
There is only one study exploring the combination of blood films together with RDT’s in diagnosing imported malaria and it was in adults (3). Of the 388 cases, 367 (95%) were diagnosed by the initial blood film. Of the 21 that weren’t diagnosed on the blood film 19 had RDT’s performed. This diagnosed a further 10 leaving only 9 cases (2.3%) not picked up by a single blood film and RDT. Only one case of P.falciparum infection was missed and this was in a partially immune individual who had already received an unspecified treatment. The remaining 8 missed cases were P.vivax and P.ovale.
If we extrapolate from this study, then if a single blood film and RDT are negative a diagnosis of malaria is extremely unlikely. This is especially true in cases of suspected P.falciparum in a non-immune patient who has not received any treatment. The most obvious criticism here, is that it is difficult to extrapolate adult data and draw conclusions relating to children. However, the available data comparing parasite counts between children and adults suggests that on average children have a comparable or higher parasite count than adults (4). This would suggest that the results seen for adults would be comparable or even favourable in children.
Because of the paucity of data overall and lack of paediatric data it is not possible to make a blanket recommendation. The risk of malaria in each individual needs to be considered in conjunction with investigation results. For more information on diagnosing malaria in children read – How to interpret malaria tests (5).
1. Ladhani S, Garbash M, Whitty CJ, Chiodini PL, Aibara RJ, Riordan FA, et al. Prospective, national clinical and epidemiologic study on imported childhood malaria in the United Kingdom and the Republic of Ireland. Pediatr Infect Dis J. 2010;29(5):434-8.
2. England PH. THE PHE MALARIA REFERENCE LABORATORYLABORATORY USER HANDBOOK. Public Health England2015.
3. Pasricha JM, Juneja S, Manitta J, Whitehead S, Maxwell E, Goh WK, et al. Is serial testing required to diagnose imported malaria in the era of rapid diagnostic tests? Am J Trop Med Hyg. 2013;88(1):20-3.
4. Mascarello M, Allegranzi B, Angheben A, Anselmi M, Concia E, Lagana S, et al. Imported malaria in adults and children: epidemiological and clinical characteristics of 380 consecutive cases observed in Verona, Italy. J Travel Med. 2008;15(4):229-36.
5. Dyer E, Waterfield T, Eisenhut M. How to interpret malaria tests. Arch Dis Child Educ Pract Ed. 2016 Apr;101(2):96-101. doi: 10.1136/archdischild-2015-309048. Epub 2016 Feb 2.
April 2016’s offering ripe for reading over the bank holiday weekend. Last text box from the 2014 BTS asthma guideline – this time on acute management, FGM and the importance of reporting colleagues who may be involved in the practice, Group A strep infection as a complication of chicken pox and some links to some good CPD sites for you and your patients.
We also welcome Dr Kat Smith this month, paediatric registrar and education fellow at King’s College Hospital, who has kindly volunteered to write monthly articles for the newsletter. It’s nice to have a fresh pair of eyes on paediatric topics and a fresh nose to the ground so to speak. Thanks, Kat, for your help.
Do leave comments below.
With thanks to Dr Kat Smith, education fellow and paediatric registrar at King’s College Hospital who answered my call last month for more writers to help me put together the monthly Paediatric Pearls newsletters.
Group A Streptococcal Infection in Chickenpox
Chickenpox in children is common and usually follows a mild and self-limiting (if somewhat itchy) course. After an incubation period of 10-21 days the first signs of illness are viral prodrome, mild pyrexia, and the classic cropping vesicular rash; the pyrexia is typically mild (38-39oC) and lasts 3-4 days.
In otherwise healthy children the most common complication of chickenpox is secondary bacterial skin infection, typically caused by scratching lesions. Whilst most of these are mild impetigo or localised cellulitis, the increased incidence of group A streptococcal (GAS) colonisation in children (around 10% are asymptomatic carriers in the throat or on skin) makes invasive GAS infection a real concern.
Secondary bacterial skin infection
This is characterised by erythema +/- tenderness around lesions. Children may be well in themselves if the infection is superficial; if they become more unwell this raises the suspicion of a more serious or invasive bacterial infection.
Serious bacterial superinfection / Invasive GAS infection
Around a third of children admitted to hospital with chickenpox have secondary skin infection, some of whom develop invasive infections such as pneumonia, osteomyelitis and septicaemia. GAS in particular can be associated with more fulminant infectious processes such as necrotising fasciitis and toxic shock syndrome (TSS); both are associated with high mortality and morbidity in children.
Features that should prompt consideration of a serious bacterial superinfection are:
- A lethargic or unwell-looking child; remember, children with chickenpox are typically uncomfortable but well.
- Spiking, high-grade pyrexia
- Pyrexia for longer than 4 days, particularly after initial improvement
- Diarrhoea or vomiting
- Soft tissue pain which seems disproportionate to other examination findings (an early sign of necrotising fasciitis)
How to prevent bacterial superinfection
Because scratching lesions is the most likely way to allow bacteria to breach the body’s normal defences, the primary aim of prevention is to limit scratching:
- Keep skin moisturised. Many parents still use calamine lotion but it is worth noting that it becomes ineffective once dry, and traditional emollients (e.g. 50:50) may be more effective.
- There is evidence that sedating antihistamines offer some benefit; chlorphenamine is licensed for this use.
- Dress children in smooth, loose, cotton clothing.
- Keep fingernails trimmed short.
- There are rare reports of NSAIDs potentially worsening skin infections in chickenpox, so ibuprofen should be used with caution. In practice, it would be unusual for a child to need ibuprofen if receiving regular paracetamol; pain or pyrexia necessitating its use in addition to paracetamol should prompt consideration of serious bacterial superinfection.
- There is no evidence to support the use of acyclovir in young, immunocompetent children with self-limiting, uncomplicated chickenpox; it does not decrease the incidence of complications.
What to do if you suspect bacterial superinfection
- Otherwise well children with evidence of few, small areas of bacterial superinfection can be managed in the community with oral antibiotics and safety-netting advice.
- Children with evidence of collection, extensive areas of bacterial superinfection, who are unwell, or have other features consistent with possible serious bacterial superinfection, need urgent referral to secondary care.
- In secondary care, unwell children with evidence of shock / sepsis need urgent resuscitation and intravenous antibiotic administration; if possible this should include clindamycin, due to its vital role in inhibiting toxin production by GAS.
- Invasive GAS infection has high mortality, and if suspected there should be a low threshold to involve senior staff, regional PICU services, and in the case of necrotising fasciitis, surgical teams (for early debridement); early use of inotropes and IVIG may also be required.
Chickenpox NICE Clinical Knowledge Summary (which I found to be the best resource by far): http://cks.nice.org.uk/chickenpox
Cohen J, Breuer J. Chickenpox treatment. Systematic review 912. BMJ Clinical Evidence.
Papadopoulos, AJ. Chickenpox. emedicineWebMD. www.emedicine.com
Re: “the increased incidence of group A streptococcal (GAS) colonisation in children (around 10% are asymptomatic carriers in the throat or on skin)”
Shaikh N, Leonard E, Martin JM. Prevalence of streptococcal pharyngitis and streptococcal carriage in children: a meta-analysis. Pediatrics. 2010 Sep;126(3):e557-64
Re. “Around a third of children admitted to hospital with chickenpox have secondary skin infection”:
Bovill B, Bannister B. Review of 26 years/ hospital admission for chickenpox in North London. Journal of Infection. 1998;36(suppl1);17-23.
Re: “necrotising fasciitis and toxic shock syndrome (TSS); both are associated with high mortality and morbidity in children.” AND “IVIG may also be required.”
Chuang YY, Huang YC, Lin TY. Toxic shock syndrome in children: epidemiology, pathogenesis, and management. Paediatr Drugs. 2005;7(1):11-25.
Re. “There is evidence that sedating antihistamines offer some benefit”
Tebruegge M, Kuruvilla M, Margarson I. Does the use of calamine or antihistamine provide symptomatic relief from pruritus in children with varicella zoster infection? Archives of Disease in Childhood. 2006:91(12);1035-1036.
Re: (continued from above) “chlorphenamine is licensed for this use.”
BNFC, available at: https://www.medicinescomplete.com/mc/bnfc/current/PHP1934-chlorphenamine-maleate.htm?q=chlorphenamine&t=search&ss=text&tot=40&p=1#_hit
Re: “if possible this should include clindamycin, due to its vital role in inhibiting toxin production by GAS.” (as well as having it drilled in to us by the microbiologists at St Thomas’):
We have seen a lot of cases of scarlet fever this year so thanks to Dr Lock for his text box this month on recognising and managing this strep infection. Comprehensive information on paediatric dizziness from Mr Sharma, ENT registrar, and a bit about asthma in schools and some of my own CPD on birthmarks caused by a Mum whose view that the internet knew more than me was a little unsettling – for a while. We have all been there, I’m sure.
Do leave comments below.