Demystifying Non-Patentability


The scope and ambit of non-patentable subject-matter has evolved and transformed considerably over the course of many years. The presence of these restrictions in the Patents Act, 1970 (‘the Act’) and patent statutes around the world is ubiquitous. Variation in the substance and contents of such restriction can be observed across different countries. Perhaps, this is an outcome of different public policy concerns and technical considerations. In India, these restrictions are exhaustively enumerated under Section 3 of the Act.

One of the common threads that can be observed in the restrictions contained under Section 3 of the Act is the bar on patenting methods to use certain products or carrying out certain procedures. Section 3(i) of the Act is one such ground. It places a restriction on inventions claiming “any process for the medicinal, surgical, curative, prophylactic diagnostic, therapeutic or other treatment of human beings or any process for a similar treatment of animals to render them free of disease or to increase their economic value or that of their products” from being patent eligible.

Interestingly, none of the terms mentioned in the provision have been defined in the Act. Such a vacuum has led to some confusion regarding the scope of the different methods mentioned therein. Fortunately, the Madras High Court has brought much needed clarity regarding one of the methods mentioned in Section 3(i): diagnostic methods. In Chinese University of Hong Kong v. Assistant Controller of Patents & Designs, 2023 SCC OnLine Mad 63721, the Court went into jurisprudential depth to address the issue of what amounts to “diagnostic methods”.

A brief history of “diagnostic methods” and the Act

Section 3(i) of the Act, as it stands today, is an outcome of the Patents (Amendment) Act, 2002.2 It introduced diagnostic procedures to the scope of Section 3(i). The purpose of this provision could be an impression of public policy concerns over monopolising diagnostic methods that could otherwise benefit public health. Alternatively, it could also reflect concerns regarding the absence of industrial applicability of diagnostic methods, which was also the reason for its exclusion in the TRIPS Agreement.3

The Patent Office Manual, 2019 defined diagnostic methods in para as those tests which identify the nature of a medical illness. Curiously, this was not the case in the previous patent manuals. The 2005 Manual excluded patent eligibility of only in vivo diagnostic methods. The subsequent 2008 and 2010 versions of the Patent Manual also contained similar provisions. Surprisingly, the same was removed from the current 2019 Guidelines.

The ruling of the Madras High Court

The ruling of the Court was an outcome of an appeal that arose out of a refusal of the Patent Application for an invention titled “Fetal Genomic Analysis from a Maternal Biological Sample”. Briefly stated, the subject application disclosed a method for determination of fetal fraction concentration. Upon examination, the patent office was of the view that the claimed subject-matter disclosed a diagnostic method and therefore, refused the grant of patent. The patent office mainly relied upon the disclosures in the specification which stated the potential use or application of the claimed method in diagnosing fetal chromosomal aberration and other diseases or conditions.

Challenging this, the patent applicant approached the Madras High Court asserting that determination of fetal fraction concentration is not a diagnostic method, since, it does not per se diagnose any disease. It was further asserted by the applicant that the term “diagnostic” under the Act must be interpreted as diagnostic methods for treatment. The applicant further contended that the methods of diagnosis in Section 3(i) of the Act must be interpreted as limited to those performed on the human body and therefore, exclude in vitro diagnostic methods.

On diagnosis and treatment

The Court proceeded to deconstruct and analyse Section 3(i) of the Act to determine the meaning of the provision. It held that “diagnostic” should not be confined only to those treatments for human beings which render them free from disease. The Single Judge highlighted that the provision uses the disjunctive “or” and pronoun “them”. Therefore, since treatment can be undertaken for treatment of a disease as well as other prophylactic purposes, the term “diagnostic” must necessarily encompass both.

Broadening the scope further, the Single Judge emphasised that the use of the term “other treatment” in Section 3(i) is indicative of the legislative intention of construing the term “treatment” widely. When viewed from this perspective, the forms of treatment mentioned in Section 3(i) must guide the interpretation of the term “diagnostic”, in line with the interpretative principle of noscitur a sociis. In doing so, the Court observed that in terms of Section 3(i), “diagnostic” is limited only to those methods which disclose pathology relevant for treatment of human beings.

On in vivo diagnosis

Addressing the argument regarding exclusion of in vivo diagnosis, the Court considered the TRIPS Agreement and related negotiations, the Patents Office Manual, and the jurisprudence at the European Patent Office (EPO). The Court, while acknowledging that the earlier patent manuals limited the ineligibility only to in vivo methods, held that the current manual does not limit the ineligibility in any such manner. The Court further held that manuals are not determinative of the scope of the exclusion and at most, is indicative of the way the patent office understood the provision.

The Court could not find any indication in Article 27(3) of the TRIPS Agreement and its travaux préparatoires that supported the exclusion as advanced by the applicant. Considering European jurisprudence on this issue, the Court discussed the decision of the European Board of Appeals (‘EboA’) regarding the corresponding provisions in the European Patent Convention.4 The EBoA propounded a 4-step test5 for the determination as to whether a method is diagnostic or not and held that those methods which are limited to the first three constitutive method steps would be patent eligible. That said, in case the inevitable result of the test leads to diagnosis, the absence of the fourth deductive step would not assist the invention to proceed for grant.

In contrast, the High Court observed that the four-step test may not be a suitable practice in India. This is because unlike in vivo diagnosis, in vitro diagnosis does not require the presence of a medical practitioner for the first three steps. This would, therefore, allow circumvention of Section 3(i) of the Act by way of artful drafting.

Court’s approach

The Court held that if the claims of an invention disclose a process to make a diagnosis for treatment, it would be patent ineligible. Contrarily, if the process so disclosed does not uncover any pathology, it would not be diagnostic. The Court further held that diagnostic tests need not definitively identify a disease. Referring to screening tests, it was held that screening tests could also fall within the ambit of diagnostic methods if they can identify the existence of a disease and other relevant characteristics and details. Mere classification of a test as a screening test is not sufficient for it to evade Section 3(i) of the Act. Therefore, the litmus test for evaluating whether an invention discloses a diagnostic method is whether the test is inherently and per se capable of identifying the disease, disorder, or condition for treatment of the person. If a person skilled in the art is not positioned to diagnose the disease through the process or method claimed in the invention, then regardless of the title of the patent application, it would not attract Section 3(i) of the Act.

Applying the same to the facts of the case, the Court highlighted that determination of fetal fraction concentration is related to diagnosis, but not “diagnostic per se”. Further testing would be necessary for the identification of a disease. Therefore, since the claimed invention was per se incapable of identifying a disease, the Court held that Section 3(i) of the Act was not attracted.

Evolution of “diagnostic methods” in other jurisdictions

The discretion provided in the TRIPS Agreement to member States regarding the inclusion of diagnostic methods within non-patentable subject-matter has led to divergent global trends. Countries having different economic, social, and political policies have distinct positions on the aspect of public health. Accordingly, they deal with this ground of non-patentability with different approaches.

Australian patent law does not contain a bar on patentability of diagnostic methods. It permits grant of patent to those inventions which are a result of human action and are not occurring naturally.6 In 2021, the Federal Court of Australia upheld the patentability of diagnostic methods in Ariosa Diagnostics Inc. v. Sequenom Inc.7 The invention under scrutiny therein was a method of non-invasive prenatal blood testing. Since the testing method was a process of detection and not a per se naturally occurring product, the Court held that the subject invention had economic significance and practical utility and therefore, qualified for grant of patent.

Similarly, the Canadian Patents Act also does not explicitly bar the patentability of diagnostic methods. The Canadian Intellectual Property Office issued guidelines on patentable subject-matters,8 pursuant to the direction of the Canadian Federal Court.9 The guidelines specify that diagnostic methods which involve testing, identification, detection of a sample would be patentable.

In the United States of America, patent eligibility of diagnostic methods has been the subject of considerable judicial attention. In Mayo Collaborative Services v. Prometheus Laboratories Inc.,10 the Supreme Court of the United States (SCOTUS) held that natural laws and their application cannot be patented. A claimed invention must have additional features which add non-obvious features to a natural phenomenon to be considered for patent eligibility.


Diagnostic methods are sine qua non for medical practitioners in their quest for gathering information to prevent, detect, treat and monitor diseases or conditions. The advancement of medicine and healthcare may even be attributed to improvements in the efficiency of the methods of diagnosis. Clearly, diagnostic methods are crucial for patient care and medical research. Promoting innovation in such a cutting-edge field would be beneficial for public health. That said, incentivising innovation must not compromise public health. A balance must be struck. To this effect, the Madras High Court observed that there is a case to consider options such as restricting the scope of expression “diagnostic” under Section 3(i) of the Act to in vivo methods and compulsory licensing provisions may provide counterbalancing. However, considering this issue to be within the legislature’s domain, the Court refrained from venturing any further. Nevertheless, the ruling of the Madras High Court has brought much needed clarity as to the scope of the term “diagnostic methods” in the context of Section 3(i) of the Act.

*Partner, LKS Attorneys

**Associate, LKS Attorneys

1. 2023 SCC OnLine Mad 6372

2. Patents (Amendment) Act, 2002.

3. UNCTAD-ICTSD, Resource Book on TRIPS and Development (2005) p. 384..

4. ECLI:EP:BA:2005:G000104.20051216. plz check not found

5. The four-step test laid down by the EBoA is: (i) examination phase involving the collection of data; (ii) comparison of data with their standard values; (iii) finding any deviation during comparison: presence of symptoms; and (iv) attribution of deviation to a particular clinical picture.

6. D’Arcy v. Myriad Genetics Inc., 2015 HCA 35.

7. [2021] FACF 101

8. Government of Canada, Canadian Intellectual Property Office, Patentable Subject-Matter under the Patent Act <>.

9. Yves Choueifaty v. Attorney General of Canada, 2020 FC 837.

10. 2012 SCC OnLine US SC 28 : 182 L Ed 2d 321 : 132 S Ct 1289 566 US 66 (2012).

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