Bilo da zna krvnu grupu bilo da ne zna, pregled počinje.

It is a fixed Serbian pattern meaning whether ... or ..., often with the nuance regardless of whether.

So:

• Bilo da zna krvnu grupu
• bilo da ne zna

together mean something like whether they know their blood type or not.

This structure is very common when you want to say that the result in the main clause stays the same in both cases.

It comes from the verb biti historically, but in a sentence like this, it is best understood as part of the fixed expression bilo da.

So for a learner, the most useful approach is:

• learn bilo da ... bilo da ... as a set pattern
• do not try to interpret bilo here as an ordinary past-tense verb meaning was

Also, notice that bilo does not change for gender or number here. It stays the same because the whole phrase functions like a conjunction.

Because da introduces a clause with a finite verb.

Here, after bilo da, we get full clauses:

• zna krvnu grupu
• ne zna

So da is needed.

Compare:

• bilo da zna, bilo da ne zna = whether he/she knows, or doesn’t know
• but with simple nouns or adjectives, Serbian can use other patterns without da

In this sentence, da is necessary because what follows is a verbal clause.

In this structure, repeating the verb is normal and natural:

• bilo da zna ... bilo da ne zna

This gives a balanced whether ... or not pattern.

In English, you might feel tempted to compress it, but Serbian often prefers to repeat the verbal idea in these paired constructions. It sounds complete and idiomatic.

Because Serbian is a pro-drop language. Subject pronouns are often omitted when the verb form and context already make the meaning clear.

Here, zna is 3rd person singular, so the subject is something like:

• he
• she
• the patient
• the person
• sometimes a generic one

The exact subject comes from context, so Serbian does not need to say it explicitly.

Because krvnu grupu is in the accusative case, not the nominative.

Base form:

• krvna grupa = blood type / blood group

After the verb znati when it takes a direct object, that object goes into the accusative:

• zna krvnu grupu = knows the blood type

So:

• nominative: krvna grupa
• accusative: krvnu grupu

Both words change because this is a feminine noun phrase.

Good question. Svoju is possible, but it is often omitted when the meaning is obvious.

So both can work:

• zna krvnu grupu
• zna svoju krvnu grupu

The version without svoju is very natural because everyone understands that the person is talking about their own blood type.

Serbian often leaves out possessives when they are clear from context.

Because in Serbian, the negative particle ne is usually written separately from verbs.

So:

• zna = knows
• ne zna = does not know

This is the normal spelling pattern for most verbs.

A learner should get used to:

• ne znam
• ne zna
• ne idemo
• ne mogu

There are a few common exceptions elsewhere in the language, but here the standard form is definitely ne zna.

Because the bilo da ... bilo da ... part is a subordinate clause placed before the main clause.

Structure:

• subordinate part: Bilo da zna krvnu grupu bilo da ne zna
• main clause: pregled počinje

Serbian normally separates that introductory subordinate section from the main clause with a comma.

So the comma marks the boundary between:

• the condition/concession-like frame
• the main statement

Pregled is in the nominative singular and it is the subject of the main clause.

Main clause:

• pregled počinje = the examination begins

So:

• pregled = subject
• počinje = verb

This is a straightforward subject + verb structure.

Because Serbian has no articles.

English distinguishes between:

• the examination
• an examination

Serbian does not do that with separate words like the or a/an. The listener understands from context whether pregled means:

• the examination
• an examination
• the check-up

In this sentence, context makes it sound like the examination/check-up.

Počinje is the present tense, 3rd person singular, of the imperfective verb počinjati.

It means:

• begins
• is starting
• starts

So:

• pregled počinje = the examination begins / starts

This is a normal present-tense statement, especially in instructions, procedures, or general descriptions.

It can sound like:

• a general rule
• a scheduled action
• an immediate procedural statement

Yes, it sounds natural, especially in a formal, procedural, or medical context.

Words like:

• krvna grupa
• pregled

already place the sentence in a medical or administrative setting.

The whole sentence has a slightly official tone, like something you might read in instructions, guidelines, or hear in a clinical setting.

Yes. A common alternative would be:

• Bez obzira na to da li zna krvnu grupu ili ne, pregled počinje.

That also means regardless of whether they know their blood type or not, the examination begins.

Compared with the original:

• bilo da ... bilo da ... is compact and elegant
• bez obzira na to da li ... ili ne is more explicit

Both are correct. The original sentence is perfectly natural.