A pyrogenicity test method and assay of endotoxins allows for rapid and ultrahigh sensitivity testing of parenteral pharmaceuticals or medical devices that contact blood or cerebrospinal fluid by employing a Limulus Amoebocyte Lysate (LAL) assay monitored with a photonic-crystal biosensor. The photonic-crystal biosensor is capable of determining the presence of endotoxins in a test sample by detecting shifts in the resonant condition of an open microcavity affected by the changes in the refractive index of the analyte solutions used.