We were very interested to read the article by Wolf et al1 titled “Lymphocyte–White Blood Cell Count [L/WCC] Ratio: A Quickly Available Screening Tool to Differentiate Acute Purulent Tonsillitis From Glandular Fever.” We agree that a rapidly available and cost-effective screening tool would undoubtedly be useful in the detection of glandular fever. Wolf and coauthors comment that the L/WCC ratio had a sensitivity of 90% and a specificity of 100% for the detection of glandular fever and that the “specificity and sensitivity of this test seem to be better than the mononucleosis spot test itself.” However, such a statement is misleading; the group used the Monolatex test (Biokit SA, Barcelona, Spain), one of the commercially available monospot testing kits, as their diagnostic criterion standard. The Monolatex test has a sensitivity of 93.9% and a specificity of 98.3% against viral titers for the detection of Epstein-Barr virus.2 Therefore, the test will have a number of false-positives and false-negatives and will hence render the sensitivity and specificity of the L/WCC ratio less accurate than is suggested in Wolf and colleagues' article. To get true sensitivities and specificities for the L/WCC ratio, it would be necessary to compare this ratio with Epstein-Barr virus–specific serologic tests, as suggested by the authors. We carried out a similar audit in our hospital. We looked at 100 patients who had undergone a Monolatex test. Our results showed that an L/WCC ratio of greater than 0.35 is 81.0% sensitive and 93.8% specific for the detection of a positive Monolatex test result.
Smale EL, Mcdonald S, Dhar V. Differentiating Tonsillitis From Glandular Fever: Is the Lymphocyte–White Blood Cell Count Ratio Any Help?. Arch Otolaryngol Head Neck Surg. 2007;133(9):952. doi:10.1001/archotol.133.9.952-a