Many sentences have "the" in front of the "onset",
the onset of the winter, of the war, ... etc
but in the medical literature (an easy search from
scholar.google.com), many sentences are stated as below
(1) In some countries, however, the time from onset of the condition to a diagnosis can be years - helen branswell, STAT, "A stubborn medical mystery: Was pandemic flu vaccine tied to an increase in narcolepsy cases?," 5 July 2018
(2) We report the youngest known molecularly identified patient suffering of severe desminopathy characterized by infantile onset of cardiac arrhythmia - G Piñol-Ripoll et al. 2009
Are these expressions (without an article) correct or incorrect ? Shouldn't they be
(1) ... the time from the/an onset of the condition ...
(2) ... characterized by the/an infantile onset of cardiac ...