- The Honest Answer on a Numeric Passing Score
- Why "Passing" Means Two Components
- What Has and Has Not Been Verified
- Question Style: What a Passing Performance Looks Like
- The Content You Must Master
- Fees, Retakes, and the Cost of Missing the Mark
- Timing Your Preparation Around the Application
- After You Pass: Validity and Revalidation
- Frequently Asked Questions
- A numeric passing standard for the Public Health Laboratory Director exam was not verified in accessible American Board of Bioanalysis sources.
- The complete PHLD(ABB) credential requires BOTH General Knowledge and Public Health Microbiology; passing one does not substitute for the other.
- Items are four-option multiple choice, and ABB's item-writing guidance favors application and scenario questions over recall.
- Two retakes are permitted after an initial failure; after three failures, you wait two years and reapply with added education or training.
The Honest Answer on a Numeric Passing Score
Most candidates searching for the passing score want a single number: a percentage or a scaled score they can aim for. For the Public Health Laboratory Director credential, designated PHLD(ABB), that number could not be verified. The American Association of Bioanalysts (AAB) and its examining body, the American Board of Bioanalysis (ABB), did not publish a numeric passing standard, component question counts, exam durations, or pass rates in the issuer sources that were accessible when this article was verified.
That matters, because many sites will happily hand you a confident "you need 70%" figure. Be skeptical of any such claim for this credential unless it cites ABB directly. Other credentials share the PHLD acronym and publish very different standards; borrowing their cut scores would mislead you. If you want to see what the available data does and does not say, our companion piece on the PHLD pass rate walks through the same verification limits.
Why "Passing" Means Two Components
The single most important structural fact about passing is this: the complete PHLD(ABB) credential requires both the General Knowledge examination and the Public Health Microbiology examination. Neither component substitutes for the whole credential. You are not "passing the PHLD" until both components are successfully completed.
That reframes the question. Instead of asking "what score do I need," ask "what do I need to demonstrate in each of two distinct bodies of knowledge?" One component tests the management and regulatory side of running a laboratory; the other tests the technical microbiology and public health content you would be accountable for as a director. A candidate strong in bacteriology but weak in CLIA regulation, or the reverse, has a real gap to close.
| Component | What It Covers | Preparation Topics |
|---|---|---|
| General Knowledge | Laboratory director management and regulatory responsibilities | CLIA '88; Financial Laboratory Management and Employment Law; General Laboratory Management; Laboratory Safety, OSHA, and Disaster Preparedness |
| Public Health Microbiology | Technical and public health microbiology content | Bacteriology; Environmental Microbiology; Parasitology; Mycology; Virology/Molecular Microbiology; Epidemiology in the Community; Immunology of Infectious Diseases; Quality Control/Quality Assurance |
For a deeper look at how these areas map out, see our complete guide to all 12 PHLD content areas.
What Has and Has Not Been Verified
Transparency is more useful than false precision here, so this section separates what is established from what is not.
Established from ABB and AAB sources
- The credential requires both General Knowledge and Public Health Microbiology.
- ABB administers the examinations, generally in spring and fall.
- Item-writing guidance specifies four-option multiple-choice questions and favors application and scenario items.
- Current weighted Content Outlines and reference lists are supplied after eligibility approval.
- Fee, eligibility, retake, and revalidation rules are published (covered below).
Not verified in accessible sources
- A current numeric passing standard for either component.
- Current question counts and exam durations per component.
- Pass rates.
Question Style: What a Passing Performance Looks Like
Because the numeric threshold is unknown, the more actionable lever is understanding the question format. ABB's item-writing guidance calls for four-option multiple-choice questions and favors application and scenario items. In practice, that means a passing performance depends less on reciting definitions and more on choosing the best action in a realistic situation.
Consider the kinds of judgment calls a director faces. A scenario item might describe a laboratory facing a regulatory finding, a safety incident, or an unusual cluster of specimens, and ask which response is most appropriate. Four plausible options will be offered, and distinguishing the best from the merely acceptable requires genuine command of the underlying rules and science.
How to Read a Scenario Item
Work these steps on every practice question until they become automatic.
- Identify which of the two components the scenario belongs to: management/regulatory or technical microbiology.
- Find the governing rule or principle before looking at the options.
- Eliminate options that are unsafe, noncompliant, or outside a director's authority.
- Choose the option that is both correct and most complete, not just defensible.
If the difficulty of this format concerns you, our article on how hard the PHLD exam really is discusses where candidates tend to struggle.
The Content You Must Master
The twelve domain lines below are unweighted preparation topics. They are not twelve official combined examination domains, and they are not an exhaustive statement of current exam coverage. Domains 1 through 4 reflect the headings from AAB's General Knowledge for the Laboratory Director online-course listing; Domains 5 through 12 reflect the eight published headings from AAB's Review Manual for Public Health Microbiology (2012 edition). Your official weighted outline arrives after eligibility approval and should override any assumption made here.
General Knowledge preparation topics
Domain 1: CLIA '88
The regulatory backbone of a director's role. Expect scenario questions about who is responsible for what.
- Director responsibilities for high-complexity testing
- How qualification and personnel requirements shape staffing decisions
- Proficiency testing obligations and responding to deficiencies
Domain 2: Financial Laboratory Management and Employment Law
Directors manage budgets and people, and exams test whether you can do so lawfully.
- Budgeting, cost control, and reimbursement considerations
- Employment law principles in hiring, discipline, and termination
Domain 3: General Laboratory Management
The operational judgment that holds a laboratory together.
- Staffing, training, and competency assessment
- Workflow, communication, and policy development
Domain 4: Laboratory Safety, OSHA, and Disaster Preparedness
Safety and continuity planning are director-level accountabilities.
- OSHA requirements relevant to laboratory settings
- Emergency and disaster preparedness planning
Public Health Microbiology preparation topics
Domains 5-9: The Organism and Methods Core
Bacteriology, Environmental Microbiology, Parasitology, Mycology, and Virology/Molecular Microbiology form the technical heart of the second component.
- Bacteriology: identification, susceptibility concepts, and reportable pathogens
- Environmental Microbiology: water, food, and environmental sample concerns
- Parasitology and Mycology: recognition, specimen handling, and clinical relevance
- Virology/Molecular Microbiology: detection approaches and interpretation
Domains 10-12: The Public Health Frame
These topics tie the laboratory to the community it serves.
- Epidemiology in the Community: outbreak recognition and surveillance reasoning
- Immunology of Infectious Diseases: serology and immune response interpretation
- Quality Control/Quality Assurance: maintaining reliable results across all disciplines
For a structured approach to working through all of this material, see the PHLD study guide and the one-page PHLD cheat sheet for rapid review.
Fees, Retakes, and the Cost of Missing the Mark
Since you cannot target an exact score, understand the consequences of falling short. The official ABB fee schedule lists a USD 420 application fee, USD 355 for an individual examination component, and USD 525 for General Knowledge plus one technical discipline taken on the same day. The figure of USD 945 is simply the arithmetic subtotal of the application fee plus the same-day examination fee. It is not an advertised package and not an all-in preparation budget.
| Item | Published Amount |
|---|---|
| Application fee | USD 420 |
| Individual examination component | USD 355 |
| General Knowledge plus one technical discipline, same day | USD 525 |
| Application plus same-day examinations (arithmetic subtotal only) | USD 945 |
For the full financial picture, including costs beyond these fees, review the PHLD certification cost breakdown.
The retake rules
The ABB FAQ permits two retakes after an initial failure. To keep your file open, a retake must occur within the next two administrations or one year, whichever is longer. After three failures, you must wait two years and reapply with evidence of additional education or training. These rules make a first-attempt pass worth planning for, because a stumble costs both money and months.
Key Takeaway
Because outcomes hinge on an undisclosed threshold, your safest strategy is breadth. Prepare every one of the twelve topics to a working level rather than perfecting a few, since a gap in either component can leave the whole credential incomplete.
Timing Your Preparation Around the Application
Preparation for this exam is shaped by the application calendar. ABB advises starting the application 16 to 20 weeks before an examination, with supporting documentation normally due 8 to 10 weeks before it. Your study plan should begin during the application window, not after it, because you will not receive your weighted Content Outline until eligibility is approved.
Eligibility itself is demanding. Standards effective December 28, 2024 provide routes for a CLIA-qualified director, a qualifying Ph.D. or Sc.D., and accepted clinical or professional doctorates. All require 32 acceptable chemistry or biological-science semester hours. Experience includes four qualifying years within the preceding ten, including two years directing or supervising high-complexity testing and two years of specified laboratory training or experience that include one year in public-health or clinical microbiology. ABB has explicitly suspended the 20-CE eligibility prerequisite pending CMS enforcement, so it is not currently an active requirement. Full details are in our PHLD requirements guide, and scheduling specifics are in the PHLD exam dates article.
Regulatory Foundation (Domains 1 and 4)
- Start with CLIA '88 and safety/OSHA because they underpin every management scenario.
- Use this window to complete your application while the material is fresh.
Management Core (Domains 2 and 3)
- Cover financial management, employment law, and general operations.
- Review your official Content Outline as soon as it arrives and re-weight your plan.
Technical Microbiology (Domains 5-9)
- Allocate more time to your weakest organism group.
- Practice with scenario questions rather than rereading text.
Public Health Integration (Domains 10-12)
- Connect epidemiology, immunology, and QC/QA back to earlier topics.
- Run full-length mixed practice sessions on the practice test site.
This is a sequencing suggestion tied to the application timeline, not an official schedule. Adjust it to your own background; a working microbiologist may compress the technical weeks, while a clinician new to regulation may expand the first block.
After You Pass: Validity and Revalidation
Success on both components is the beginning of an ongoing obligation. Initial certification is valid through December 31 of the award year. Maintaining it requires annual revalidation and 24 acceptable continuing-education contact hours per two-year PEER cycle. Knowing this upfront helps you judge the long-term commitment; our ROI analysis and salary guide explore whether the investment pays off, and the PHLD jobs overview describes the roles that value the credential.
If you are still orienting yourself to the credential, start with what PHLD certification is, then return here. When you are ready to test your readiness, the PHLD practice test site offers scenario-style questions that mirror the four-option application format ABB favors.
Frequently Asked Questions
A current numeric passing standard for the Public Health Laboratory Director exam was not verified in accessible American Board of Bioanalysis sources. Avoid relying on any specific cut score unless it is supplied by ABB directly, and prepare broadly across all preparation topics instead.
Yes. The complete PHLD(ABB) credential requires both components. Neither one substitutes for the whole credential, so both must be successfully completed.
ABB permits two retakes after an initial failure. A retake within the next two administrations or one year, whichever is longer, keeps your file open. After three failures, you wait two years and reapply with evidence of additional education or training.
ABB's item-writing guidance specifies four-option multiple-choice questions and favors application and scenario items, so expect to apply knowledge to realistic laboratory situations rather than simply recall facts.
Current weighted Content Outlines and reference lists are supplied after eligibility approval. The older General Knowledge outline in ABB's Item Writer Guide dates to June 2014 and should not be treated as current or complete.