One approach is meta-analysis of its citations that can be effectively used.

To understand patent quality you need to forget the number of patents an use different indicators. Many large enterprises only patent their findings to protect their secrets.

You can use indicators such as percentage of innovative sales derive from patenting or you can use thpercentage of patents that were accepted by the market (that were commercialize).

You can see my paper for some insights: https://www.researchgate.net/publication/279156280_A_methodology_to_measure_innovation_in_European_Union_through_the_national_innovation_system

Article A methodology to measure innovation in European Union throug...

An alternate approach to assess the quality of patents is to determine (compute) the cash flows generated by the patents. A patent that supports the firms innovation capabilities create a competitive advantage in the marketplace, and generate positive cash flows and value for the firm.

Thanks.

 Measurement of cash flow generated from patents is very difficult specially in large engineering organisations. Patent may be related to a sub-assembly of a small product, where as these organisations are dealing with large infrastructure development projects.

In my opinion, a few alternative approaches could be Brand Image of the company, Market share, Levels of Customer Satisfaction, Customer Retention, Customer Loyalty and of-course  business generated from new products.

Even these parameters are not perfect, because Nokia enjoying 80% market share suddenly goes out of the market, because it could not timely respond to the changing needs of the mobile market.

Thus, a measurement of quality of patent should also address, how fast it could be commercialized and create a new niche for itself.   

Thanks for nice views. We will explore alternatives, starting from citations.