10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
These 10 free PHLD questions are organized by exam domain, so you can see how each part of the Public Health Laboratory Director (PHLD) blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: CLIA '88
Question 1
A laboratory routinely sends certain bacterial isolates to a reference laboratory for confirmatory identification. An isolate in an active CLIA proficiency testing event reaches that referral point. The microbiology supervisor argues that sending it out would satisfy the requirement to handle proficiency specimens like patient specimens. Which instruction is compliant?
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Correct answer: B - Complete the usual in-house work, but do not refer the proficiency specimen.
Domain 2: Financial Laboratory Management and Employment Law
Question 2
An assay generates 4,000 reportable results annually. Referral costs $48 per reportable result. Bringing the assay in-house would add $90,000 in annual fixed costs and $18 per reportable result in variable costs. Finance would also allocate $40,000 of existing building overhead to the assay, but that overhead will be paid under either arrangement. Capacity, performance, and turnaround requirements are equivalent, and no other costs change. On a relevant-cost basis, which recommendation is supported?
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Correct answer: C - Bring testing in-house; annual costs would fall by $30,000.
Domain 4: Laboratory Safety, OSHA, and Disaster Preparedness
Question 3
A reference laboratory confirms Brucella in an isolate that a technologist manipulated outside a biological safety cabinet earlier that day. The work included vortexing a suspension; several coworkers were in the room. Nobody recalls a spill, splash, or sharps injury, and the material has now been secured. What should lead the director's immediate response?
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Correct answer: D - Initiate a task- and location-based exposure assessment with occupational health.
Domain 5: Bacteriology
Question 4
Three residents of a long-term-care facility develop pneumonia within one week. Legionella testing is requested for a patient whose L. pneumophila serogroup 1 urinary antigen test is negative. His sputum contains few leukocytes and abundant oral flora but meets the validated volume and transport requirements for Legionella testing. A technologist proposes rejecting it under the routine bacterial sputum policy. How should the director resolve the request?
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Correct answer: D - Accept the sputum for Legionella culture and validated molecular testing.
Domain 7: Parasitology
Question 5
Six weeks after receiving red-cell transfusions, an asplenic adult develops fever and hemolytic anemia. A thin blood film initially reported as showing possible malaria contains pleomorphic intraerythrocytic rings, occasional extracellular forms, and rare four-membered tetrads. The patient has not traveled to a malaria-endemic region. Which provisional identification best fits the film?
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Correct answer: C - Babesia species
Domain 8: Mycology
Question 6
A kidney-transplant recipient has pulmonary infiltrates and several ulcerated skin lesions. Urine Histoplasma antigen is positive. A skin biopsy shows large, thick-walled yeasts with broad-based buds rather than small intracellular yeasts. Which explanation most coherently reconciles the antigen result with the tissue findings?
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Correct answer: A - Blastomycosis with a cross-reactive Histoplasma antigen result.
Domain 9: Virology/Molecular Microbiology
Question 7
In a real-time PCR assay, an exogenous internal control is added after extraction, immediately before amplification. Neither the target nor this control amplifies in one patient extract. The same control amplifies in water with the same master mix, and the run's positive and negative controls are acceptable. Fresh control added to a second aliquot of the undiluted extract also fails; dilution of that extract restores control amplification. This pattern most strongly localizes the problem to:
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Correct answer: D - Amplification inhibition carried in the patient extract.
Domain 10: Epidemiology in the Community
Question 8
An outbreak team interviews all 100 attendees at a catered event using the same illness definition. Of 30 people who ate a seafood salad, 24 became ill. Of 70 who did not eat it, 7 became ill. No attendees are missing exposure or outcome data. Which statement belongs in the team's preliminary cohort analysis?
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Correct answer: B - The risk ratio is 8.0; salad consumption warrants investigation as an associated exposure.
Domain 11: Immunology of Infectious Diseases
Question 9
Prenatal screening at 11 weeks yields a reactive treponemal immunoassay, nonreactive RPR, and reactive TP-PA. Records document adequate treatment for syphilis six years earlier, an appropriate subsequent RPR decline, and eventual RPR seroreversion. The patient has no compatible symptoms or ongoing exposure risk. Her obstetrician asks whether the reactive screening result requires another treatment course. The most appropriate interpretation is:
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Correct answer: A - Persistent treponemal antibodies after adequate treatment; these findings do not require retreatment.
Domain 12: Quality Control/Quality Assurance
Question 10
During review of a quantitative assay, today's two control results are +2.3 SD and −0.4 SD from their respective means. The approved procedure uses the classic Westgard multirule scheme: 1_2s, 1_3s, 2_2s, R_4s, 4_1s, and 10x. During the preceding nine runs, each control level alternated above and below its mean, always within 1 SD. All other acceptance checks pass. What disposition is justified?
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Correct answer: B - Accept the run after documenting the warning review.