Diagnostic patent exclusion covers in vitro methods capable of enabling diagnosis, not just in vivo testing.

Section 3(i) of the Patents Act, 1970 was interpreted to exclude diagnostic processes even where the claimed method is performed in vitro rather than on the human body. Reading the claims with the complete specification, the Madras High Court noted that the nucleic-acid analysis method was inherently capable of identifying sequence imbalance and enabling diagnosis of fetal chromosomal aneuploidy, so it fell within the diagnostic exclusion. The court further stated that the exclusion is not confined to definitive diagnosis or to in vivo methods, and that the patent application was therefore rightly refused.

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Issues: Whether the claimed non-invasive in vitro method for measuring sequence imbalance in a biological sample from a pregnant female subject is a diagnostic process falling within the patent exclusion under Section 3(i) of the Patents Act, 1970.

Analysis: Section 3(i) excludes processes for diagnostic treatment of human beings, and the expression "diagnostic" is not confined to in vivo methods. The statutory text, read in context, does not support limiting the exclusion to diagnosis practised on the human body, nor does it warrant excluding in vitro methods merely because they are performed outside the body. The language of Article 27(3)(a) of the TRIPS Agreement and the contrasting wording of Article 52(4) of the European Patents Convention, 1973 were considered, but they did not justify reading a bodily-practice limitation into the Indian provision. The complete specification and amended claims showed that the method uses size-based analysis of nucleic acid fragments from maternal blood to identify sequence imbalance and enable diagnosis of fetal chromosomal aneuploidy; the embodiments disclosed that a diagnosis can be made from the claimed process, even if it is not definitive or comprehensive. The method was therefore capable, per se, of uncovering pathology for treatment and was not saved by the disclaimers or by the fact that some earlier patent manuals appeared narrower.

Conclusion: The claimed invention is a diagnostic method excluded by Section 3(i) of the Patents Act, 1970, and the refusal of the patent application was upheld.

Ratio Decidendi: A process is patent-ineligible as diagnostic under Section 3(i) when, on the claims read with the complete specification, it is inherently capable of making a diagnosis for treatment of human beings, and the exclusion is not limited to in vivo methods or to definitive diagnosis.

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