Background: In schizophrenia, pathway-genotypes may be constructed by combining interrelated
immune biomarkers with changes in specific neurocognitive functions that represent aberrations
in brain neuronal circuits. These constructs provide an insight on the phenome of schizophrenia and
show how pathway-phenotypes mediate the effects of genome X environmentome interactions on the
symptomatology/phenomenology of schizophrenia. Nevertheless, there is a lack of knowledge how to
construct pathway-phenotypes using Partial Least Squares (PLS) path modeling and Soft Independent
Modeling of Class Analogy (SIMCA).
Aims: This paper aims to provide a step-by-step utilization guide for the construction of pathwayphenotypes
that reflect aberrations in the neuroimmune - brain circuit axis (NIBCA) in deficit schizophrenia.
Methods and Results: This NIBCA index is constructed using immune biomarkers (CCL-2, CCL-11,
IL-1β, sIL-1RA, TNF-α, sTNFR1, sTNFR2) and neurocognitive tests (Brief Assessment of Cognition in
Schizophrenia) predicting overall severity of schizophrenia (OSOS) in 120 deficit SCZ and 54 healthy
participants. Using SmartPLS path analysis, a latent vector is extracted from those biomarkers and cognitive
tests, which shows good construct reliability (Cronbach alpha and composite reliability) and replicability
and which is reflectively measured through its NIBCA manifestations. This NIBCA pathwayphenotype
explains 75.0% of the variance in PHEMN (psychotic, hostility, excitation, mannerism and
negative) symptoms. Using SIMCA, we constructed a NIBCA pathway-class that defines deficit schizophrenia
as a qualitatively distinct nosological entity, which allows patients with deficit schizophrenia to
be authenticated as belonging to the deficit schizophrenia class.
Conclusion: In conclusion, our nomothetic approach to develop a nomological network combining
neuro-immune and neurocognitive phenome markers to predict OSOS and cross-validate a diagnostic
class generated replicable models reflecting the key phenome of the illness, which may mediate the effects
of genome X environmentome interactions on the final outcome phenome features, namely symptomatology