Molecular Testing for Chlamydia and Gonorrhoea: From Laboratory NAAT to Point-of-Care Workflows

Nucleic acid amplification testing (NAAT) can be performed within conventional laboratory workflows, while newer molecular systems can bring testing closer to the patient.

The important question is therefore not simply whether a test is “laboratory-based” or “point-of-care.”

It is how the complete testing pathway — from patient and anatomical site to specimen, assay, testing location, quality system and result — supports the intended clinical use.

C. trachomatis and N. gonorrhoeae infections may be asymptomatic, meaning the absence of symptoms does not necessarily exclude infection.

When testing is indicated according to the applicable clinical or screening pathway, molecular methods can detect pathogen nucleic acid from appropriate specimens without relying solely on clinical signs and symptoms.

NAAT has therefore become an important foundation of CT/NG diagnostic testing.

However, molecular testing is not simply an instrument-and-reagent question.

The result begins with the testing indication and specimen.

An analytically capable assay cannot compensate for an inappropriate specimen or an anatomical site that was not sampled when sampling from that site is clinically indicated.

NAAT stands for nucleic acid amplification test.

Rather than relying on visual identification of an organism, NAAT detects specific nucleic-acid sequences associated with the target pathogen and amplifies those sequences so they can be detected.

Real-time polymerase chain reaction, or qPCR, is one widely used form of nucleic acid amplification technology.

For CT/NG testing, molecular assays may detect C. trachomatis, N. gonorrhoeae, or both within the same testing workflow.

Depending on the assay and platform, molecular testing may be performed in:

These locations should not be viewed simply as a hierarchy from older to newer testing.

They represent different ways of organizing molecular diagnostics.

STI diagnostic pathways may begin in different ways.

This distinction is important because both chlamydia and gonorrhoea can occur without obvious symptoms.

Molecular testing therefore supports more than investigation of symptomatic disease. It may also form part of screening or testing pathways defined by relevant clinical guidance.

The decision to test — and which anatomical sites to test — should follow the appropriate clinical and public-health guidance rather than being determined by the molecular assay alone.

One of the most important principles in molecular STI testing is that the specimen is part of the diagnostic system.

CT and NG testing may involve specimens such as urine or swabs collected from relevant genital or extragenital anatomical sites, depending on the patient, exposure history, clinical indication and validated intended use of the assay.

The testing pathway can therefore be viewed as:

Testing only one anatomical site does not automatically provide information about another site.

Similarly, laboratories should not assume that every specimen type is interchangeable across molecular assays. Specimen claims, collection devices, transport conditions and assay validation should be considered for the particular testing system being used.

Specimen collection does not always need to follow a conventional clinician-collected model.

For appropriate CT/NG testing pathways, self-collection can provide an additional approach to specimen collection.

This is distinct from self-testing.

These terms should not be used interchangeably.

Self-collection can potentially change where and how people access specimen collection while the analytical testing itself may still occur in a professional laboratory or another controlled testing environment.

The complete pathway still requires appropriate specimen instructions, identification, transport or transfer where applicable, testing, result reporting and linkage to care.

Conventional laboratory NAAT remains an important model for CT/NG testing.

A simplified workflow may include:

Centralized laboratories can support established quality systems, trained laboratory personnel, instrumentation, connectivity and potentially higher testing volumes.

Depending on the laboratory and platform, specimens may be processed individually, in batches or through automated workflows.

This model can be highly effective when specimen transport, laboratory capacity and result-return pathways are well established.

But the analytical run time of an assay is only one component of total turnaround.

The complete pathway may also include specimen collection, transport, accessioning, batching, processing, validation, reporting and communication of results.

Molecular point-of-care testing changes the location and organization of the testing pathway, not necessarily the fundamental principle of nucleic-acid detection.

A simplified molecular POCT pathway may look like:

Some molecular POCT systems integrate several conventional laboratory steps into a closed or simplified workflow.

This may reduce specimen movement and the number of handoffs between collection and result availability.

However:

Point-of-care does not automatically mean better.

An appropriate molecular POCT implementation still needs to consider:

• analytical performance;
• specimen compatibility;
• operator training;
• internal and external quality processes;
• contamination control where relevant;
• instrument maintenance;
• result interpretation;
• connectivity and documentation;
• throughput;
• cost and resource requirements; and
• integration into the clinical pathway.

Centralized laboratory testing and molecular POCT should therefore be considered complementary testing models, not automatically competing technologies.

There is no single testing model that is optimal for every environment.

The appropriate question is not:

“Which technology is better?”

It is:

“Which testing model best supports the intended diagnostic and service pathway?”

Molecular STI testing does not have to stop at two targets.

A focused molecular assay may answer a clearly defined question:

Is C. trachomatis or N. gonorrhoeae detected?

Broader multiplex molecular panels can expand the number of pathogens investigated within a testing workflow.

Depending on their intended use and validated target composition, multiplex STI or reproductive-health panels may include additional organisms such as Trichomonas vaginalis, Mycoplasma genitalium, herpes simplex viruses and other targets.

Some laboratory qPCR panels may extend further, incorporating numerous targets within a broader STI or reproductive-tract testing strategy.

This creates a continuum:

But increasing the number of targets does not automatically make a molecular panel more clinically useful.

More targets ≠ automatically better testing.

The value of a multiplex panel depends on whether its target composition supports the intended diagnostic question and whether detected organisms can be interpreted appropriately in the population and specimen being tested.

This becomes increasingly important as panels expand beyond established STI pathogens to organisms that may have more complex relationships with colonization, carriage, reproductive-tract microbiology or disease.

Laboratories should therefore evaluate not only:

“How many targets does the panel detect?”

but also:

“Why are these targets being tested, and how will each result be interpreted and used?”

The choice between focused and broader molecular testing can be approached as a diagnostic-design question.

But broader testing also introduces additional questions:

• Is every target clinically relevant to the intended population?
• Is the specimen appropriate for every target?
• What does a positive result mean?
• Does detection represent infection, colonization or another biological state?
• Will every result change clinical management?
• How should coinfections or multiple detections be reported?
• Are additional confirmatory or follow-up investigations required?

Panel selection should therefore begin with the diagnostic question, not with the maximum number of targets available.

Multiplex real-time PCR can amplify and detect more than one molecular target within a testing workflow.

For STI testing, this can allow laboratories to investigate several pathogens simultaneously rather than performing a completely separate assay for every organism.

However, multiplex assay design becomes more complex as the number of targets increases.

Laboratories evaluating broader multiplex qPCR solutions should consider:

A panel with more than ten targets may be technically impressive, but target count alone is not a sufficient selection criterion.

This distinction is particularly important for N. gonorrhoeae.

A conventional CT/NG NAAT primarily addresses a pathogen-detection question:

It does not automatically answer:

Which antimicrobial agents is this organism susceptible or resistant to?

Gonococcal antimicrobial resistance is a major public-health concern.

Phenotypic antimicrobial susceptibility testing and molecular approaches designed specifically to investigate resistance therefore address a different diagnostic question from routine pathogen detection.

Some emerging or specialized molecular approaches may detect particular resistance-associated genetic markers, but detecting selected markers should not automatically be treated as equivalent to comprehensive phenotypic susceptibility information.

Laboratories and clinicians should interpret pathogen detection and resistance characterization according to the capabilities, limitations and intended use of the relevant test.

The key distinction is:

Pathogen detection ≠ antimicrobial susceptibility determination.

Malaysia’s national guidance for the management of sexually transmitted infections includes molecular testing within the diagnostic approach to CT and NG and recognizes that specimen selection can vary according to patient and anatomical context.

This reinforces an important laboratory principle:

The assay should be selected as part of the complete clinical and specimen pathway, not in isolation.

Malaysia’s diagnostic environment may include tertiary and hospital laboratories, private laboratories, primary-care settings and other healthcare environments with different testing volumes, infrastructure and access to centralized molecular testing.

As molecular platforms become increasingly capable of supporting both centralized and decentralized workflows, laboratories should consider where testing is best performed while maintaining appropriate analytical performance, quality assurance and linkage of results to care.

Local implementation should follow current Malaysian guidance, applicable regulatory requirements and the validated intended use of the selected diagnostic system.

When evaluating molecular STI testing, laboratories can work through the following sequence:

Selecting a molecular STI solution involves more than comparing assay specifications.

A laboratory introducing or expanding CT/NG or multiplex STI testing may need to evaluate:

• testing demand;
• current molecular infrastructure;
• target coverage;
• specimen workflow;
• extraction requirements;
• qPCR or integrated-platform compatibility;
• laboratory throughput;
• decentralized-testing requirements;
• operator training;
• quality-control strategy;
• result reporting;
• reagent logistics; and
• technical support.