  We construct a physics-agnostic approach to the neutron star (NS) equation of
state (EoS) based on a sound speed model, which connects both low-density
information from nuclear theory and high-density constraints from perturbative
QCD (pQCD). Using this approach, we study the impact of pQCD calculations on NS
EoS that have been constrained by astrophysical observations. We find that pQCD
affects the EoS mainly beyond the densities realized in NS. Furthermore, we
observe an interesting interplay between pQCD and astrophysical constraints,
with pQCD preferring softer EoS for the heaviest NS while recent NICER
observations suggest the EoS to be stiffer. We explore the sensitivity of our
findings to pQCD uncertainties and study the constraining power of pQCD if
future observations of heavy NS were to suggest radii larger than 13 km.
