FDA defines/clarifies the terms intended use and indication for use in the guidance document : 

Evaluation of Substantial Equivalence: Predicate device.  But when you look at many 510K, FDA states the indication for use and not the intended use (maybe because the intended use is included in the Indication for use?)

FDA seems flexible in their acceptance of the definitions. 

Do you define them separately in your QMS? and why? What would be the reason to combine them?  

Any other thoughts? 

FDA defines/clarifies the terms intended use and indication for use in the guidance document : 

Evaluation of Substantial Equivalence: Predicate device.  But when you look at many 510K, FDA states the indication for use and not the intended use (maybe because the intended use is included in the Indication for use?)

FDA seems flexible in their acceptance of the definitions. 

Do you define them separately in your QMS? and why? What would be the reason to combine them?  

Any other thoughts? 

I'll forego a detailed explanation of the difference between intended use vs. indications for use since that looks to be outside the scope of your question since you indicate that you already understand the difference and are instead seeking advice regarding the practical [e.g., 510(k), QMS, etc.] implications of these concepts.

In a nutshell, yes, the intended use and indications for use need to be stated separately in a 510(k) and in the QMS.  I explain further below.

In a 510(k), both the "intended use" (i.e., the general purpose of the device or its function as shown by the labeling) and the "indications for use" (i.e., the disease or condition the device will diagnose, treat, prevent, cure or mitigate, including a description of the patient population for which the device is intended) are in fact distinctly established; though perhaps not always obviously so.  Specifically, the intended use is linked to, and intrinsically governed/established by the applicable classification regulation (e.g., 21 CFR 8XX.XXXX) that must be stated in the 510(k).  In contrast, the indication(s) for use is/are linked more so to the corresponding FDA Product Code (if at all) which must also to be stated in the 510(k), but in any event, distinctly stated by way of the FDA Form 3881 and in the labeling.

All this said, in practice for the purposes of 510(k) substantial equivalence, FDA tells us that the indications for use are generally encompassed within the intended use.  Thus, their distinction can in practice be nebulous.  For example, sometimes the indications will simply be the same as the intended use in simple cases where the sponsor has elected not to striate particular indications within the intended use; indeed, such granularity isn't always required.  So in that instance, the reason for combining them is simply that no specific indications have been devised beyond the general intended use.  But oftentimes, specific indications are indeed distinguished under the overarching general intended use; in that case, they need to be clearly stated to meet the intent of a 510(k).

Regarding the QMS, the subject device's intended use principally affects the QMS by way of the corresponding device risk class.  Specifically, that risk class (see the subject device's classification regulation) dictates the nature and complexity of the QMS and of the QMS documents. For example, certain FDA class I devices are exempt from design controls, while others are exempt from FDA GMP altogether (except for complaint files and records).  I'm a strong proponent that this distinction is essentially required to be stated in the QMS's Quality Manual, though that notion has been a source of intense debate.

And going deeper down to the level of the indications for use and their effect (if any) on the QMS, such effects are often of a more granular nature.  For example, the required type and extent of device developmental documentation will be affected by the indications, such as the need for prospective clinical data regarding some indications, while others only need bench data.  In that context, the targeted indications are to be distinguished in the design inputs (where design controls apply).  Another QMS example is that the indications for use can also have an impact on the nature and extent of post-market surveillance.  Still other QMS examples could be given.

FDA defines/clarifies the terms intended use and indication for use in the guidance document : 

Evaluation of Substantial Equivalence: Predicate device.  But when you look at many 510K, FDA states the indication for use and not the intended use (maybe because the intended use is included in the Indication for use?)

FDA seems flexible in their acceptance of the definitions. 

Do you define them separately in your QMS? and why? What would be the reason to combine them?  

Any other thoughts? 

I'll forego a detailed explanation of the difference between intended use vs. indications for use since that looks to be outside the scope of your question since you indicate that you already understand the difference and are instead seeking advice regarding the practical [e.g., 510(k), QMS, etc.] implications of these concepts.

In a nutshell, yes, the intended use and indications for use need to be stated separately in a 510(k) and in the QMS.  I explain further below.

In a 510(k), both the "intended use" (i.e., the general purpose of the device or its function as shown by the labeling) and the "indications for use" (i.e., the disease or condition the device will diagnose, treat, prevent, cure or mitigate, including a description of the patient population for which the device is intended) are in fact distinctly established; though perhaps not always obviously so.  Specifically, the intended use is linked to, and intrinsically governed/established by the applicable classification regulation (e.g., 21 CFR 8XX.XXXX) that must be stated in the 510(k).  In contrast, the indication(s) for use is/are linked more so to the corresponding FDA Product Code (if at all) which must also to be stated in the 510(k), but in any event, distinctly stated by way of the FDA Form 3881 and in the labeling.

All this said, in practice for the purposes of 510(k) substantial equivalence, FDA tells us that the indications for use are generally encompassed within the intended use.  Thus, their distinction can in practice be nebulous.  For example, sometimes the indications will simply be the same as the intended use in simple cases where the sponsor has elected not to striate particular indications within the intended use; indeed, such granularity isn't always required.  So in that instance, the reason for combining them is simply that no specific indications have been devised beyond the general intended use.  But oftentimes, specific indications are indeed distinguished under the overarching general intended use; in that case, they need to be clearly stated to meet the intent of a 510(k).

Regarding the QMS, the subject device's intended use principally affects the QMS by way of the corresponding device risk class.  Specifically, that risk class (see the subject device's classification regulation) dictates the nature and complexity of the QMS and of the QMS documents. For example, certain FDA class I devices are exempt from design controls, while others are exempt from FDA GMP altogether (except for complaint files and records).  I'm a strong proponent that this distinction is essentially required to be stated in the QMS's Quality Manual, though that notion has been a source of intense debate.

And going deeper down to the level of the indications for use and their effect (if any) on the QMS, such effects are often of a more granular nature.  For example, the required type and extent of device developmental documentation will be affected by the indications, such as the need for prospective clinical data regarding some indications, while others only need bench data.  In that context, the targeted indications are to be distinguished in the design inputs (where design controls apply).  Another QMS example is that the indications for use can also have an impact on the nature and extent of post-market surveillance.  Still other QMS examples could be given.

FDA defines/clarifies the terms intended use and indication for use in the guidance document : 

Evaluation of Substantial Equivalence: Predicate device.  But when you look at many 510K, FDA states the indication for use and not the intended use (maybe because the intended use is included in the Indication for use?)

FDA seems flexible in their acceptance of the definitions. 

Do you define them separately in your QMS? and why? What would be the reason to combine them?  

Any other thoughts?