Thursday, August 16, 2018

Evaluation of a Visual Triage for the Screening of MERS-CoV Patients


With the Hajj scheduled to begin in 3 days time, and with more than 2 million religious pilgrims from around the globe gathering in the Holy Cities of Saudi Arabia, the way that the Saudi MOH screens for potential MERS-CoV cases is of particular interest.
As we've seen previously, respiratory infections are the most commonly reported illness among religious pilgrims (see  EID Journal: ARI’s In Travelers Returning From The Middle East).
This study also found that  `Pneumonia is the leading cause of hospitalization at Hajj, accounting for approximately 20% of diagnoses on admission.’
Four years ago, in EID Journal: Respiratory Viruses & Bacteria Among Pilgrims During The 2013 Hajj, we looked at another study that examined a small group of French pilgrims (n=129) both before and after attending the Hajj, and compared nasal swabs.  They found: 
. . .  that performing the Hajj pilgrimage is associated with an increased occurrence of respiratory symptoms in most pilgrims; 8 of 10 pilgrims showed nasal or throat acquisition of respiratory pathogens. 
It is against this confusing backdrop that medical authorities must evaluate, and hopefully accurately identify and isolate, potential MERS cases among hundreds of thousands of symptomatic travelers presenting with a variety of respiratory symptoms.
While laboratory tests are available, they generally take between 24-48 hours to get the results,  and it usually requires two negative tests - 24 to 48 hours apart - to rule out MERS, during which time the patient should be isolated. 
Doable when you are dealing with a few dozen suspected cases, but impractical on a much grander scale.  Instead, the Saudi MOH has developed a scoring system - based on visible symptoms, and exposure history - to decide who to isolate and test as a potential MERS case.
The $64 question is:  Does it work?
The answer, as provided by prolific MERS researcher and former KSA Deputy Minister of Health,  Ziad Memish, MD et al.,  in a new analysis published this week in NMNI, is not particularly well.
Evaluation of a Visual Triage for the Screening of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Patients

Sarah H. Alfaraj, MBBS, Jaffar A. Al-Tawfiq, MD, Philippe Gautret, MD, Mishal Ghazi Alenazi, MBBS, Ayed Yahya Asiri, MBBS, Ziad A. Memish, MD

Open Access


The emergence of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in September 2012 in Saudi Arabia had attracted the attention of the global health community. Recently in the beginning of 2017, the Saudi Ministry of Health released a visual triage system with scoring to alert healthcare workers in emergency departments and hemodialysis units for the possibility of occurrence of MERS-CoV infection in their patients.

Patients and Methods

This is a retrospective analysis of the visual score of the Saudi Ministry of Health to determine its sensitivity and specificity. The study included all cases from 2014 to 2017 in a MERS-CoV referral center in the city of Riyadh, the capital of Saudi Arabia.


During the study period, there were a total of 2435 suspected MERS cases. Of these cases 1823 (75%) tested negative and the remaining 25% tested positive for MERS-CoV by PCR assay. The application of the visual triage score revealed a similar percentage of MERS-CoV and non-MERS CoV patients with each score from 0 to 11.
The percentage of patients with the cut-off score of > 4 was 75% in patients with MERS Cov infection and 85% in patients without MERS-CoV infection (P =0.0001). The sensitivity and specificity of this cut off score for MERS-CoV infection were 74.1% and 18.6%, respectively.


The sensitivity and specificity of the scoring system was low and further refinement of the score is needed for better prediction of MERS-CoV infection.
The two main measures of the accuracy of any diagnostic test are sensitivity and specificity.
  • Sensitivity is defined as the ability of a test to correctly identify individuals who have a given disease or condition.
  • Specificity is defined as the ability of a test to exclude someone from having a disease or illness.
This visual scoring system failed to identify more than 25% of MERS cases, and at the same time more than 80% of `tagged' patients were negative for the virus.

The authors provide two strategies to improve screening:
Firstly, revise the case definition after careful review of the data available to the MoH for 5 years and secondly invest in developing a highly sensitive and specific point of care (POC) testing in the EDs and haemodialysis units where the results will be available in 1-2 hours [24–26].
The authors were particularly blunt in their assessment (bolding mine) of the current system.
The  current  study  conducted  on  a  large  number  of  patients  shows  that  clinical  scoring  is not predictive  of  MERS  infection. 
Our  results  are  robust  and  confirm  that  MERS  cannot  be distinguished from other respiratory infections based on  risk factors  and clinical features.  Thus all  patients with  non-specific  symptoms  in  a  MERS  endemic  area  will  have  to  be  isolated  until MERS can be ruled out by rapid PCR testing.
All of which adds weight to the notion that a substantial number of MERS cases may be going undiagnosed in Saudi Arabia, and elsewhere in the world.  We've seen estimates that many - perhaps even most - MERS cases go undetected.

While we've been lucky in the past, with no large MERS outbreaks linked to the Hajj, the possibility of seeing one or more infected pilgrims returning to their home countries while silently incubating the virus remains a genuine concern.

All of which will have public health officials around the world particularly on alert for the next 30 days.

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