Microbiología Médica y Diagnóstico

Assessment of Loop-Mediated Isothermal Amplification (LAMP) Assay for Rapid Detection of Mycoplasma Pneumoniae Infection in Paediatric University Hospital

Abstract

Eiman M. AbdulRahman, Amal Mohammed Sayed, Reham HA Yousef, Bassant Salah Saad Meligy and Samar Ahmed Mohammed Altohamy

Introduction: Community-acquired pneumonia (CAP) caused by M. pneumoniae affect 3%-10% of children. It is not possible to spot M. pneumoniae infection depending entirely on clinical signs and symptoms. Correct identification of M. pneumoniae infections is crucial to initiate proper antibiotic therapy. The role of culture is questionable as this organism is fastidious. Diagnostic accuracy of serology depends on the specimen collection time. IgM can usually be tracked within one week after the onset of clinical illness, followed by IgG two weeks later. Nucleic Acid Amplification Techniques (NAATs) are proved to be the “new gold standard”. Loop-Mediated Isothermal Amplification (LAMP) amplifies DNA of mycoplasma in less than an hour under isothermal conditions with the use of six primers in a single tube. The amplified products can be visualized by naked eye as turbidity or fluorescence.

Aim: To assess the diagnostic value of LAMP assay compared to serum Mycoplasma IgM for rapid detection of M. pneumoniae.

Materials and methods: A 6-months study was conducted on hospitalized children diagnosed with community acquired pneumonia (CAP) admitted to Cairo University specialized pediatric hospital (CUSPH). M. pneumoniae IgM was done on serum samples by RD-Ratio Diagnostics ELISA kit, Germany. LAMP assay was done on nasopharyngeal swabs using Loopampᵀᴹ RNA/DNA, Eiken Chemical, Japan. Kappa measure of agreement was calculated to assess the concordance between LAMP and Mycoplasma IgM.

Results: 90 hospitalized children with CAP were included in the study. Serum IgM was positive in 27(30%) of cases. LAMP assay was positive in 33 cases (36.7%). The sensitivity of LAMP was 85.2%, the specificity was 84.1%, PPV was 69.7%, NPV 93.0% with AUC=0.847. The agreement between serology and LAMP was good K=0.652 with 95% CI (0.487-0.816).

Conclusion: LAMP technique is a rapid, sensitive and specific method for diagnosis of M. pneumoniae. Combination of LAMP assay and serology may be optimal for the diagnosis of M. pneumoniae infection.