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Utility of quantitative loop mediated isothermal amplification (qLAMP) assay for the diagnosis of invasive
Sreeram Chandra Murthy Peela1, Sujatha Sistla1
1Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education & Research, Puducherry, India.
Purpose:
Quantitative LAMP (qLAMP) assay is one of the recent and emerging diagnostic tests for infectious diseases. Only a few studies exist comparing this assay with quantitative real-time PCR (qPCR) for the diagnosis of invasive pneumococcal disease (IPD).
Aim:
To compare the diagnostic performance of qLAMP assay with qPCR targeting autolysin gene for the diagnosis of invasive pneumococcal disease.
Methods:
Ninety six blood samples and 73 CSF samples from patients clinically suspected with community acquired pneumonia and acute meningitis were tested by qPCR and qLAMP assays using previously published primers and protocols. The qPCR was considered as the gold standard test and the diagnostic performance was assessed by calculating sensitivity, specificity, positive and negative predictive values, and kappa coefficient for the level of agreement between the tests. Chi-squared/Fisher exact test was used to compare categorical variables (positive/negative).
Results:
Thirty two blood samples and 22 CSF samples were positive by qPCR while 24 and 20 samples were positive by qLAMP assay respectively. The sensitivity of qLAMP assay was only 86.4% and 75% when tested on CSF and blood samples respectively. However, the qLAMP assay was in substantial to almost perfect agreement when compared with qPCR. The results were statistically significant in both sample types (P < 0.001).
Conclusions:
The performance of qLAMP assay can vary based on the specimen type. It has very high specificity and had substantial to almost perfect agreement, and thus may be an alternative to qPCR for the diagnosis of IPD.
Insights
Quantitative loop-mediated isothermal amplification (qLAMP) shows high specificity and agreement for diagnosing invasive pneumococcal disease (IPD). While sensitivity varies by specimen, qLAMP offers a potential alternative to quantitative real-time PCR (qPCR).
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Quantitative loop-mediated isothermal amplification (qLAMP) is an emerging diagnostic tool for infectious diseases.
- Limited studies compare qLAMP with quantitative real-time PCR (qPCR) for invasive pneumococcal disease (IPD) diagnosis.
Purpose of the Study:
- To evaluate and compare the diagnostic performance of qLAMP assay against qPCR for IPD detection.
- To assess qLAMP's accuracy using blood and cerebrospinal fluid (CSF) samples.
Main Methods:
- Ninety-six blood and 73 CSF samples from suspected IPD patients were tested using both qPCR and qLAMP assays.
- qPCR served as the gold standard; diagnostic performance metrics included sensitivity, specificity, predictive values, and agreement (kappa coefficient).
Main Results:
- qPCR detected 32/96 blood and 22/73 CSF samples positive for IPD.
- qLAMP identified 24/96 blood and 20/73 CSF samples positive.
- qLAMP sensitivity was 75% for blood and 86.4% for CSF, with substantial to near-perfect agreement with qPCR (P < 0.001).
Conclusions:
- qLAMP assay performance is specimen-dependent.
- The assay demonstrates high specificity and substantial to near-perfect agreement with qPCR.
- qLAMP presents a viable alternative diagnostic method for invasive pneumococcal disease.
