Another method to assess completeness of reporting, and the adequacy and thoroughness of case investigations, is to monitor diagnostic effort. This is done by reviewing laboratory records to determine if health care providers are obtaining appropriate laboratory specimens to confirm or rule out suspected cases of disease reported to the surveillance system. Monitoring diagnostic effort provides an answer to the question, “Is anyone suspecting the diagnoses of these diseases?” Tracking the number of specimens submitted to a laboratory even if none are positive, provides good evidence that the diagnoses are being considered, even if no cases are found. For example, tracking submission of laboratory requests for viral isolates, IgM antibody tests, and paired sera testing for measles, mumps, and rubella suggests that clinicians are looking for cases of disease and the diagnoses are being considered. Tracking laboratory requests for testing of bacterial cultures from suspected cases of diphtheria and pertussis prior to antibiotic administration serve similar purposes. Under these circumstances, the absence of reported cases is more likely to reflect the true absence of disease. Hospital discharge records can also be reviewed to identify discharge diagnoses for diseases of interest; this has been done to identify cases of meningitis due to H. influenzae, and tetanus.