💡 Detailed Explanation
「〜いかんにかかわらず」 means "regardless of ~" or "irrespective of ~", emphasizing that the specific nature, details, or state of the preceding noun is irrelevant to the subsequent situation or action. It is highly formal. The other options are also N1-level grammar points expressing similar meanings but with subtle differences:
1. 「〜のいかんを問わず」 is extremely close in meaning and formality, literally meaning "without asking about the specifics/details of ~". It is often interchangeable with 「〜いかんにかかわらず」, but the latter is sometimes preferred for more general statements of policy or fact.
2. 「〜を問わず」 is slightly less formal and means "regardless of ~" in a broader sense, often used for simpler, more direct characteristics like age, gender, or presence/absence of something.
3. 「〜にかかわらず」 is the most general and least formal of the options, simply meaning "regardless of ~".
In this context, where 「容態 (condition)」 implies varying and detailed states, 「いかんにかかわらず」 is the most precise and natural fit to convey that all specific aspects of the condition are disregarded.