How many of the 175 questions on the CST exam are actually scored toward your pass/fail result?

150 are scored and 25 are unscored pretest items. Only 150 of the 175 items count toward your score. The remaining 25 are unscored pretest questions the NBSTSA is field-testing for future exams. Because they are seeded randomly and look identical to scored items, you should answer every question as if it counts.

Which organization owns and administers the CST certifying examination?

The NBSTSA. The NBSTSA (National Board of Surgical Technology and Surgical Assisting) writes and administers the CST exam. The AST is the separate professional membership association that publishes curriculum and banks CE credits; it does not own the certification exam.

Because the CST exam imposes no penalty for guessing, the best strategy for an item you cannot answer is to:

Eliminate any distractors you can and record your best guess. With no guessing penalty, a blank is a guaranteed miss while a guess gives at least a 25% chance on a four-option item. Eliminating one or two distractors raises those odds, so you should always record an answer for every question.

The CST passing standard of roughly 98 of 150 scored questions is best described as:

A criterion-referenced fixed competency bar. The CST uses a criterion-referenced standard: a fixed competency bar set through formal standard-setting, independent of how other candidates score. Clearing roughly 98 of 150 scored items (about 65%) means you meet the bar regardless of anyone else's performance.

CST Certified Surgical Technologist Exam Ove | Free Guide 2026

Key Takeaways

The CST exam is built and administered by the NBSTSA, a credentialing body legally separate from the AST membership association.
The exam delivers 175 multiple-choice questions, of which 150 are scored and 25 are unscored pretest items seeded randomly throughout.
Candidates have a single 4-hour (240-minute) session and must answer at least 98 of the 150 scored questions correctly to pass.
All items are four-option, single-best-answer multiple choice with no penalty for guessing, so every question should be answered.
Testing is delivered through PSI at brick-and-mortar test centers or via PSI live remote (online) proctoring.
The three content domains are Perioperative Care (91 items), Ancillary Duties (26 items), and Basic Science (33 items).

The CST Credential and Who Owns It

The Certified Surgical Technologist (CST) is the nationally recognized entry-level credential for the surgical technologist who works at the sterile field as the scrub during operative procedures. The exam is created, owned, and administered by the National Board of Surgical Technology and Surgical Assisting (NBSTSA).

A point candidates routinely confuse — and one the exam itself never tests directly but that shapes every interaction you have — is that the NBSTSA is not the AST. The Association of Surgical Technologists (AST) is the professional membership organization that publishes the Core Curriculum and processes continuing-education credits. The NBSTSA is the independent credentialing body that writes and scores the certifying examination. You apply to the NBSTSA to test; you join the AST for membership benefits and to bank CE credits.

The NBSTSA is accredited by the National Commission for Certifying Agencies (NCCA), which is why hospitals treat the CST as a legitimate competency credential rather than a course-completion certificate.

Exam Format and Logistics

The CST examination is a computer-based test (CBT) delivered by PSI. You sit it in one timed block.

Detail	Specification
Administering body	NBSTSA
Total questions	175 multiple-choice items
Scored questions	150
Unscored pretest items	25 (seeded randomly, indistinguishable)
Time limit	4 hours (240 minutes)
Item format	4 options, single best answer
Passing standard	~98 of 150 scored correct (~65%)
Delivery	PSI test center or PSI live remote proctoring
Guessing penalty	None

The 25 pretest items are the single most important format fact for test-day psychology. They are unscored questions the NBSTSA is field-testing for future forms, scattered invisibly among the 150 that count. Because you cannot tell a scored item from a pretest item, the correct strategy is to treat every question as if it counts and never let an oddly difficult or out-of-blueprint question rattle you — it may simply be an experimental item that will not affect your result.

Because there is no penalty for guessing, you must record an answer for all 175 questions. A blank is a guaranteed miss; a guess on a four-option item carries a 25% chance of being correct. Eliminate one or two distractors and that climbs sharply.

Every item is single best answer — there are no 'select all that apply,' matching, or fill-in items on the live CST. That format constraint matters because it means each question has exactly one defensible key, and the distractors are usually plausible-but-wrong alternatives drawn from common student errors (for example, naming the wrong antiseptic for an eye prep, or the wrong position for a procedure). Reading every option before committing is essential; the second-best choice is engineered to look right to an underprepared candidate.

The four hours are generous enough — about 1 minute 22 seconds per item — that careless misreads, not time pressure, are the more common cause of lost points.

Scoring and the Passing Standard

The CST is scored against a criterion-referenced standard, not a curve. Your result does not depend on how other candidates performed on the same day; it depends only on whether you cleared a fixed competency bar set through a formal standard-setting (Angoff-style) study. In practice the passing standard sits at roughly 98 of the 150 scored questions, about 65%. The 25 pretest items contribute nothing to your score.

A few scoring realities worth internalizing:

A scaled score is reported; the NBSTSA converts raw correct answers to a scale so that different exam forms are equivalent in difficulty. You will see a pass/fail determination and a scaled number, not a simple percentage.
Failing candidates receive diagnostic feedback by content domain, telling you which of the three areas was weakest so you can target a retake.
The ~65% threshold means you can miss roughly 52 scored questions and still pass — useful context if a block of items feels brutal. Keep moving; do not spiral.

Why the Credential Matters

The CST is the credential most operating rooms list as required or strongly preferred. Several states have enacted laws requiring surgical technologists to hold the CST (or be working toward it), and the credential is the gateway to the Certified Surgical First Assistant (CSFA) pathway later in a career. Passing demonstrates verified competence in sterile technique, instrumentation, the surgical count, and perioperative patient safety — the core of the role.

Test-Day Flow at a Glance

Understanding the rhythm of the day removes surprises. After check-in (photo ID, biometric capture, and a locker for personal items at a center, or a 360° room scan for remote testing), you are seated at a workstation and given a brief tutorial that walks through the navigation, the flag/mark feature, and the on-screen timer. The tutorial time does not count against your 240 minutes.

Once the exam starts, the 175 items present one at a time. You can move forward and backward, flag questions for review, and change answers freely until you submit. There is a running countdown clock on screen. A standard CBT comfort-break policy applies: the clock keeps running if you step away, so leaving the room costs scored time. When you submit — or when the 4 hours expire — the exam ends and a preliminary indication is followed by the official NBSTSA result after processing. The unscored pretest items are removed before your scaled score is computed, so nothing you saw that felt 'off-blueprint' can hurt a passing total.