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Predictive power of Koplik's spots for the diagnosis of measles
1Centre for Infection, HPA, London UK. dominik.zenner@hpa.org.uk
Introduction:
Measles is a major cause of mortality globally. In many countries, management of measles is based on clinical suspicion, but the predictive value of clinical diagnosis depends on knowledge and population prevalence of measles. In the pre-vaccine era with high measles incidence, Koplik's spots (KS) were said to be "pathognomonic". This study prospectively evaluated test properties and diagnostic odds ratios (OR) of KS.
Methodology:
Data including KS status were prospectively collected for a six-month period on all suspected measles cases reported to the North-West London Health Protection Unit. Saliva test kits were sent to all cases and KS test properties were analysed against measles confirmation by PCR or IgM testing (gold standard).
Results:
The positive predictive value (PPV) of clinically suspecting measles was 50%. Using KS as diagnostic tool improved the PPV to 80% and the presence of KS was associated with confirmed measles in the multi-variable analysis (OR 7.2, 95% Confidence Interval 2.1-24.9, p=0.001).
Conclusion:
We found that Koplik's spots were highly predictive of confirmed measles and could be a good clinical tool to enable prompt measles management and control measures, as action often needs to be taken in the absence of laboratory confirmation. We suggest that current clinical case definitions might benefit from the inclusion of KS.
Insights
Koplik's spots (KS) significantly improve the diagnosis of measles, increasing the positive predictive value to 80%. This clinical sign aids in prompt measles management when laboratory confirmation is unavailable.
Area of Science:
- Infectious Diseases
- Clinical Diagnostics
- Public Health
Background:
- Measles remains a significant global cause of mortality.
- Clinical diagnosis of measles is common but varies in accuracy.
- Koplik's spots (KS) were historically considered pathognomonic for measles.
Purpose of the Study:
- To prospectively evaluate the diagnostic properties of Koplik's spots (KS) for measles.
- To determine the diagnostic odds ratio (OR) of KS in suspected measles cases.
Main Methods:
- Prospective data collection on suspected measles cases over six months.
- Analysis of KS status against measles confirmation via PCR or IgM testing (gold standard).
- Evaluation of test properties and diagnostic odds ratios (OR) for KS.
Main Results:
- The positive predictive value (PPV) of clinical suspicion alone was 50%.
- Incorporating KS improved the PPV to 80%.
- Presence of KS was significantly associated with confirmed measles (OR 7.2, p=0.001).
Conclusions:
- Koplik's spots are highly predictive of confirmed measles.
- KS can serve as a valuable clinical tool for prompt measles management and control.
- Inclusion of KS in clinical case definitions is recommended.
