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Surfactant Protein A (SP-A)

Published: July 27, 2026Updated: August 25, 2026

Surfactant Protein A (SP-A) is a protein biomarker that plays a crucial role in the innate immune response within the lungs and is essential for the regulation of pulmonary surfactant homeostasis.

Quick summary

SP-A is a diagnostic biomarker for lung diseases, measured in ng/mL with a reference range of 0–43 ng/mL.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
ng/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche SP-A, Yamasa SP-A
interpretation: {"text":"Levels below the reference range may indicate conditions such as acute respiratory distress syndrome (ARDS) or certain genetic disorders affecting surfactant production.","label":"Low Levels"}; {"text":"Levels above the reference range may suggest lung diseases like IPF, chronic obstructive pulmonary disease (COPD), or other conditions causing lung tissue damage.","label":"High Levels"}

Surfactant Protein A (SP-A) is a protein primarily found in the lungs, where it contributes to the regulation of surfactant function and acts as a key component of the innate immune system. It helps in the defense against pathogens and the modulation of inflammatory responses.

The measurement of SP-A levels in blood or bronchoalveolar lavage fluid can aid in the diagnosis of various lung diseases, including idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases. Elevated levels of SP-A may indicate damage to the alveolar epithelial cells.

Clinically, SP-A is used as a diagnostic tool to assess lung injury and to monitor disease progression. Its levels can help differentiate between various pulmonary conditions and guide treatment strategies.

Frequently asked questions

What is the role of SP-A in the lungs?
SP-A plays a critical role in maintaining pulmonary surfactant homeostasis and contributes to the innate immune response by helping to defend against pathogens.
How is SP-A measured?
SP-A levels are typically measured in blood or bronchoalveolar lavage fluid using immunoassays, with a reference range of 0–43 ng/mL.
  1. 1
    Role of Surfactant Protein A in Lung DiseaseSource
  2. 2
    Surfactant Protein A as a BiomarkerSource

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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy