What Is Diagnostic Testing? A Guide Through Heart and Lung Health

Introduction: The Tests Behind Nearly Every Medical Decision

Diagnostic testing influences roughly 70% of all medical decisions in the United States, yet most patients understand very little about what these tests involve or why they were ordered. Every year, U.S. doctors request more than 14 billion lab tests, making diagnostic testing one of the most pervasive touchpoints in modern healthcare.

In plain language, diagnostic testing refers to any medical procedure used to identify, confirm, or rule out disease by analyzing biological samples or signals from the body. According to the World Health Organization, this includes blood, urine, tissue, imaging, and physiological measurements. Rather than cataloging every possible test, this guide uses heart and lung health as its organizing lens: a domain where diagnostic testing is both urgently needed and frequently misunderstood.

The urgency is real. Nearly half of U.S. adults now meet criteria for cardiovascular disease when hypertension is included, and millions of people live with undiagnosed COPD or asthma. These are precisely the conditions diagnostic testing is designed to catch. This article explains what diagnostic testing is, how key cardiopulmonary tests work together, what to expect from the process, and when to seek specialized evaluation.

What Is Diagnostic Testing? A Working Definition

Grounded in the WHO framework, diagnostic testing encompasses medical procedures that determine physiological status or detect the presence and characteristics of disease. It is distinct from routine screening. Screening looks for risk in people who feel healthy, while diagnostic testing investigates specific symptoms, abnormal findings, or known risk factors to reach a clinical conclusion.

Diagnostic tests fall into several broad categories:

• Laboratory analysis: blood, urine, and tissue samples
• Physiological measurement: EKG, spirometry
• Imaging: X-ray, CT, echocardiogram
• Functional and exercise-based testing: CPET, VO2 Max

Crucially, diagnostic tests are rarely isolated events. They are part of a clinical reasoning process in which the result of one test often points to the need for another. The scale of this field continues to grow: the global diagnostic testing market was valued at approximately $215 billion in 2026 and is projected to reach roughly $274 billion by 2034, driven by rising chronic disease prevalence and demand for early, accurate diagnosis.

Why Cardiopulmonary Diagnostic Testing Matters More Than Ever

Cardiovascular diseases account for nearly 18 million deaths annually worldwide and remain the leading cause of morbidity and mortality globally. The 2026 American Heart Association Statistics Update confirms that CVD is becoming more prevalent, more chronic, and more expensive, and that the limiting factor is no longer scientific knowledge or technology. It is the implementation and integration of the diagnostic tools already available.

The 2026 JACC Cardiovascular Statistics report reinforces this concern, noting that long-term gains in cardiovascular mortality are slowing or reversing, with persistent gaps in quality of care.

Lung disease follows a similar pattern. Spirometry remains significantly underused in primary care, contributing to misdiagnosis rates of 30 to 50% for COPD and asthma. That means millions of patients are being treated for the wrong condition or not treated at all.

The two systems overlap dangerously. COPD patients face disproportionately high rates of unrecognized heart failure and atrial fibrillation. The RED-CVD trial, published in The Lancet Public Health, found that a proactive early-detection strategy more than doubled new diagnoses of heart failure, atrial fibrillation, and coronary artery disease in patients with COPD or type 2 diabetes compared to usual care.

The Core Cardiopulmonary Diagnostic Tests and How They Work Together

Cardiopulmonary diagnostics are best understood as a connected system rather than a checklist. Each test captures a different dimension of heart and lung function, and their real diagnostic power emerges when a specialist interprets the results together. The subsections below walk through the most important tests, what each measures, and why it matters.

EKG (Electrocardiogram): The Heart’s Electrical Signature

An EKG (also written ECG) is a simple, non-invasive test that records the electrical activity of the heart using electrodes placed on the skin. It detects arrhythmias, heart rate abnormalities, evidence of prior heart attack, conduction defects, and structural changes.

Its main limitation is timing. A standard resting EKG captures only a brief snapshot, so intermittent arrhythmias that occur during activity or at night may go unseen. Holter monitors extend this by recording 24 or more hours of continuous signals, providing a fuller picture of the heart’s electrical behavior over time. Advances in AI-assisted ECG interpretation are also facilitating earlier detection of acute coronary syndrome, with some real-world implementations reporting critical turnaround times of roughly 2.9 minutes. EKG findings often serve as the entry point that prompts more comprehensive testing.

Pulmonary Function Testing (PFTs) and Spirometry: Measuring What the Lungs Can Do

Pulmonary function testing is a family of noninvasive tests measuring lung volume, capacity, airflow rates, and gas exchange. Spirometry is the cornerstone: the patient breathes into a device that measures how much air is exhaled and how quickly, generating data used to diagnose obstructive conditions like asthma and COPD as well as restrictive conditions.

The underuse of spirometry is a primary driver of the 30 to 50% misdiagnosis rate for these conditions. Specialized extensions add precision: FeNO testing measures exhaled nitric oxide to assess airway inflammation, methacholine challenge testing evaluates airway hyperreactivity, and exercise challenge testing detects exercise-induced bronchoconstriction. Lung function data is also essential context for interpreting cardiopulmonary exercise results, since the two systems cannot be fully understood in isolation.

Cardiopulmonary Exercise Testing (CPET): The Most Comprehensive Cardiopulmonary Diagnostic

CPET (also called CPEX or VO2 testing) is a specialized stress test that measures the body’s physiological response to exercise, simultaneously assessing cardiac, pulmonary, and metabolic function. It collects EKG data, heart rate, oxygen uptake (VO2 max), carbon dioxide output, ventilatory efficiency, and blood oxygen levels, all measured breath-by-breath during progressive exercise on a treadmill or bike.

A standard cardiac stress test primarily looks for EKG changes and symptoms. CPET goes further, quantifying how efficiently the heart and lungs work together and pinpointing where a limitation exists. The StatPearls/NIH resource describes CPET as “an often overlooked and underutilized modality” that can identify disease in patients with marginally abnormal standard diagnostics. In 2016, the American Heart Association advocated that cardiorespiratory fitness, measured via CPET, be treated as a clinical vital sign.

CPET combined with exercise stress echocardiography is valuable for diagnosing heart failure, cardiomyopathies, pulmonary arterial hypertension, valvular heart disease, and coronary artery disease. For athletes and health-conscious individuals, VO2 Max testing provides a gold-standard measurement of aerobic capacity and endurance, meaning the same test that serves clinical diagnosis also serves performance optimization.

Supporting Tests That Complete the Cardiopulmonary Picture

A comprehensive evaluation often includes additional tests:

• Arterial Blood Gas (ABG) sampling: measures oxygen and CO2 directly from an artery, providing precise data on how well the lungs oxygenate blood.
• High Altitude Simulation Testing (HAST): assesses how oxygen levels respond to the reduced-oxygen environment of air travel or high altitude.
• Resting Energy Expenditure (REE): measures caloric burn at rest, informing clinical management and exercise prescription.
• DEXA Body Scan: measures bone density, muscle mass, and body fat, offering important context since cardiovascular risk is closely linked to body composition.

These tests are most valuable when interpreted together by a specialist, not as isolated results from separate providers.

What Happens When Diagnostic Testing Is Incomplete or Delayed?

Diagnostic gaps carry real consequences. The 30 to 50% misdiagnosis rate for COPD and asthma without proper spirometry means patients may spend years on ineffective treatments while their condition quietly worsens. The COPD-cardiovascular overlap compounds this risk, leaving treatable heart failure and atrial fibrillation undetected.

Access is part of the problem. A 2026 analysis published in Science argues that diagnostic tests are overlooked in U.S. policy, with nearly half of the world’s population lacking adequate access and tests receiving less R&D investment and lower reimbursement than drugs. Many patients also face long backlogs at hospital-based facilities driven by staffing shortages and post-COVID operational strain. Every delay translates into delayed diagnosis and delayed treatment.

Receiving a referral for testing can feel alarming. It should not. Testing is an empowering step toward clarity, not a signal of concern.

What to Expect at a Specialized Cardiopulmonary Diagnostic Center

The typical patient journey begins with a referral or self-referral, followed by intake and history review, then baseline testing such as EKG and spirometry, and finally more advanced testing as indicated (CPET, PFTs, ABG). A comprehensive, specialist-overseen evaluation represents a higher standard of care than fragmented testing scattered across multiple providers.

Interpretation matters as much as the test itself. When performed correctly, many modern diagnostic tests reach accuracy levels above 95%, but that accuracy depends on test quality and clinician expertise. Specialized centers, distinct from large hospital systems, often offer a more focused environment with shorter wait times and staff dedicated exclusively to diagnostic testing.

Centers like Belmar Cardiopulmonary Diagnostic Center illustrate this model, offering EKG, spirometry, CPET, VO2 Max, PFTs, methacholine and exercise challenge testing, FeNO, ABG, HAST, and DEXA, all overseen by licensed, credentialed staff and board-certified physicians, with flexible scheduling that includes weekends and direct referral access. This quality-focused philosophy prioritizes thorough, individualized evaluation over high patient volume: a meaningful distinction for anyone navigating complex or unresolved symptoms.

The Future of Cardiopulmonary Diagnostic Testing

The field is evolving quickly. The AI in cardiology market is forecast to expand from $3.44 billion in 2026 to $49.16 billion by 2035, driven by AI-assisted ECG interpretation, echocardiography analysis, and predictive risk stratification. Decentralized testing is rising as well: over half of global diagnostics experts expect 10 to 25% of all tests to be performed at home by 2035, which makes patient education about which tests require specialist settings (such as CPET) increasingly important.

Personalized medicine is shifting care away from population averages toward patient-specific baselines. The central theme from the 2026 AHA Update, however, remains constant: the limiting factor is implementation and integration. The future depends on connecting available tools to the patients who need them.

Conclusion: Diagnostic Testing Is Where Better Health Begins

Diagnostic testing is not a bureaucratic formality. It is the clinical foundation on which accurate diagnosis, effective treatment, and long-term health management are built. With nearly half of U.S. adults carrying cardiovascular risk and millions living with undiagnosed lung disease, the real question is whether patients have access to the right tests, interpreted by the right specialists, at the right time.

EKG, spirometry, CPET, PFTs, and supporting tests are most powerful when used together as a coordinated diagnostic picture. Understanding what these tests reveal transforms a potentially anxious experience into an informed, empowering one. Early, accurate diagnosis remains the single most powerful intervention available for cardiovascular and pulmonary disease.

Take the Next Step Toward Cardiopulmonary Clarity

For patients who have been referred for cardiopulmonary testing, are experiencing unexplained shortness of breath, fatigue, or chest symptoms, or simply want a comprehensive baseline evaluation of heart and lung health, specialized diagnostic testing is the logical next step.

Belmar Cardiopulmonary Diagnostic Center offers a full range of services, from EKG and spirometry to CPET and VO2 Max testing, with flexible scheduling, weekend availability, and a patient-centered approach that prioritizes quality care over volume. BCDC accepts direct referrals and walk-in appointments when scheduling allows, helping patients bypass the long wait times common at larger regional facilities.

To schedule an appointment or consultation, call 206-730-9364 or email hello@belmarcardio.org. Diagnostic testing is not something to fear. It is something to pursue, because the information it provides puts both patients and their care teams in a far stronger position to protect long-term health.