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What is the use of the glass test?

Three Part Question

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

Clinical Scenario

A well 4 year old girl is seen in A+E with a rash and a 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.

Search Strategy

CINAHL, EMBASE and Medline 1966-4/03 using the Ovid interface and PubMed.
[exp (purpura OR purpuric) OR (petechiae OR petechial) AND (glass OR tumbler)] LIMIT to English AND human.

Search Outcome

No relevant or irrelevant papers were found.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses


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 organisations 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 abscence of petechiae with the glass tumbler test should not reassure parents as children with meningococcal diseases (and other petechial associated infectious diseases such as group B streptococcal infection) may be present without a rash or with a maculopapular rash. Relying on the abscence 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 treatment path for meningococcal disease or other infective causes, which may be inappropriate and harmful, as the child may experience 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 solely rely on this one test. More work is required to determine the sensitivity, specificity, and likelihood ratio of this oft used test.

Clinical Bottom Line

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


  1. Meningitis Research Foundation . 2002
  2. PHLS website .