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What is the use of the glass test?
  1. Ami Parikh1,
  2. Ian Maconochie2
  1. 1Specialist Registrar in Paediatric A+E, St Mary’s Hospital, London; simonvnaparikh.freeserve.co.uk
  2. 2Consultant of Paediatric A+E, St Mary’s Hospital, London

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A well 4 year old girl is seen in A+E with a rash and fever. Her parents have performed the “glass tumbler test” and she has petechiae. You wonder how reliably this test distinguishes petechiae from other skin lesions.

Clinical bottom line

  • No evidence was found to support the use of the glass tumbler test as a predictor for the diagnosis of petechiae.

Structured clinical question

In a child with a rash [patient] does a positive glass/tumbler test [test] reliably pick up petechiae [outcome]?

Search strategy and outcome

CINAHL, EMBASE, and Medline 1966–April 2003 using the OVID interface and PubMed: exp (purpuric OR purpura) OR (petechial OR petechiae) AND (tumbler OR glass). Limit to Human and English.

No relevant or irrelevant papers were found.

Commentary

The glass tumbler test is used in clinical practice and is recommended by many health organisations, including the Meningitis Research Foundation and Public Health Laboratory Service. These organistions inform parents of how to perform the glass tumbler test; by placing a glass tumbler firmly against a rash. If the parents can see the rash through the glass then the test is positive. If it is positive, parents are advised to seek medical advice immediately. 1,2

The absence of petechiae with the glass tumbler test should not reassure parents as children with meningococcal disease (and other petechial associated infectious diseases such as group B streptococcal infection) may present without a rash or with a maculopapular rash. Relying on the absence of a petechial rash could be fatal (that is, a test result which is a false negative). The converse is also true: that all children with petechiae do not have meningococcal disease (that is, a test result which is a false positive) and therefore do not necessarily need to follow that the treatment path for meningococcal disease or other infective causes, which may be inappropriate and harmful, as the child may experiences adverse side effects of treatment. The decision for the clinician is to judge the risk of serious illness in a child with the petechiae in context of the complete clinical state of the child, and not to rely solely on this one test. More work is required to determine the sensitivity, specificity, and likelihood ratio of this oft used test.

REFERENCES

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Footnotes

  • Bob Phillips

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