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EG |
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| Egypt J Pediatr Allergy Immunol |
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2012 |
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10 |
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02 |
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67-74 |
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ESP - 13 |
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Original articles |
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| Real-Time PCR in the early detection of invasive fungal infection in
immunodeficient infants and children |
| Zeinab A. El-Sayed |
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Zeinab E. Hasan |
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Rasha A.R. Nasr |
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| Background: Crucial to the diagnosis and effective therapy of invasive
fungal infection (IFI) in the immunodeficient is the early identification of the
causative agent especially in patients who lack clinical evidence of the
disease. The standard methods for the detection of fungi in clinical
specimens are direct microscopy and mycological culture. Microscopy often
lacks a satisfactory sensitivity, whereas diagnosis by mycological culture
often requires a long growth period. Studies have demonstrated the
feasibility of detecting molds and yeast in a single reaction using the
universal fungal primer. Objective: Evaluation of the role of real-time PCR
in the early detection of fungal infection in immunodeficient patients with
suspected IFI, who lack clinical evidence of the disease. Methods: This
study included 30 immunodeficiency patients suspected of having IFI; 9 with
primary and 21 with secondary immunodeficiency. All patients had at least
one host factor, but no clinical criteria according to the EORTC-MSG
definition of IFI. Twenty seven had fever and 3 had bronchopneumonia, both
not responding to broad spectrum antibiotics for 96 hrs. or more. Blood
samples were cultured for fungi and were analyzed with real-time PCR
using universal fungal primers. For positive samples of fungal infection,
aspergillus-specific primers were used for detection of aspergillus. Results:
Seventeen patients (56.7%) proved to have IFI. Blood culture detected
Candida in 2 patients only, while PCR detected Candida in another 9 and
Aspergillus in 6, thus 15/17 patients with IFI (88%) were missed by blood
culture. Blood culture for IFI diagnosis had a very low sensitivity (12%) but
had a 100% specificity and positive predictive value. The results PCR did
not vary with gender, degree of fever, immunodeficiency type, clinical
presentation or current intake of antifungal treatment. Patients with proven
IFI showed significantly increased CRP levels as compared to those without
infection. Conclusion: Real-time PCR proved superior to culture in early
diagnosis of IFI in patients with immunodeficiency before the appearance of
the characteristic clinical and imaging signs. Reliance on blood culture
alone at that stage would result in missing most of the positive cases with
consequent delay in the initiation of specific treatment. |
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