Objectives:

To evaluate the assessment of cases presented under suspicion of SARS and to estimate the impact of various case definitions.

Methods:

Descriptive study of the cases submitted between 17 March and 7 July. A two sources capture-recapture method was used. The first source consisted of cases reported by clinicians and general practitioners to community health services. Public health physicians submitted the cases for further assessment to the National Co-ordination Centre for Communicable Diseases (LCI). The other source consisted of the data base from the Reference Laboratory for SARS (Virology Dept, Erasmus MC) where clinical specimens were received. The first assessment by clinician/public health physician was compared with the assessment on the basis of the ruling case definition at that moment and with a retrospective reassessment using the latest Dutch case definition (i.e. WHO-case definition, 1 May 2003).

Results:

In the Netherlands five case-definitions were issued, reflecting the dilemmas with respect to specificity versus sensitivity within risk assessment. Seventy-two patients were submitted for SARS assessment of which 51 to the LCI, 37 to the reference laboratory; 16 patients were identified in both data bases. The three major criteria for SARS (respiratory disease, fever > 38°C and travel related risk) were met in 25 cases (34%). Using the most sensitive case definition (i.e. WHO; revised 1 May 2003) 21 cases would have required reporting for SARS-assessment as suspect cases and two patients as probable cases. Using the more specific case definitions, only nine cases would have met the criteria for reporting and SARS assessment, whereas, despite the case definitions, 52 cases were presented as serious suspect by clinician or public health physician. Risk ratios for being a suspect case were calculated comparing the presentation by the physician versus the first assessment and the reassessment. The reference laboratory performed serological testing for antibodies against SARS-CoV, as well as virus culture and PCR. None of the patients tested positive for the SARS-CoV.

Conclusions:

Even when using case definitions with a high specificity over-reporting of cases takes place. Over-reporting of cases should be taken into account when estimating and planning epidemic control resources. The non-cases would require a thorough assessment and case management as well. A centralised assessment centre is recommended.