Human Metapneumovirus Workup

Updated: Jan 18, 2017
  • Author: Aliyah Baluch, MD, MSc, FACP; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Workup

Laboratory Studies

Human metapneumovirus (hMPV) is difficult to grow in cell culture, largely explaining the delay in recognizing this pathogen, which has been causing disease for 50 years. Isolation is possible in a limited number of cell lines and requires trypsin supplementation. This is not a clinically useful mode of diagnosis given these technical limitations and the prolonged time to effectively culture hMPV.

  • Serological diagnosis is possible using enzyme-linked immunoassays (ELISA). However, seropositivity is nearly universal after early childhood, making definitive serological diagnosis reliant on seroconversion or a 4-fold titer increase on serial samples.
  • Immunofluorescence testing has been developed for hMPV and is available through commercial laboratories but is not yet widely used in clinical settings.
  • The most sensitive means of hMPV infection diagnosis is by PCR of respiratory secretions, which is currently the most commonly used method. In research settings, this technique is also being used to quantify viral load. Multiplex PCRs are being used with increasing frequency to diagnose hMPV infection and to rule out concomitant viral infections.

Given the prevalence of hMPV, more widespread availability of rapid diagnostic tests would be clinically useful.

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Imaging Studies

Although chest radiography is often obtained in patients with significant lower respiratory tract infection (LRTI), no findings distinguish hMPV from other causes of viral pneumonia or bronchiolitis. Chest CT scanning without contrast is the image of choice to evaluate for LRTI in combination with viral testing such as multiplex PCR. The most common findings of hMPV infection on CT scanning are patchy ground-glass opacities, centrilobular nodules, bronchial wall thickening, and multifocal areas of consolidation. [53] Nonetheless, these findings can be found in nearly all presentations of viral pneumonia.

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