Assessing the Diagnostic Value of X-Rays Across Medical Conditions: A Systematic Review

Abstract

Background: X-rays (plain radiography) are one of the most ubiquitous imaging modalities in medicine, with over 3.6 billion diagnostic imaging exams (predominantly X-rays) performed annually worldwide[1]. Chest radiographs (CXRs) alone account for an estimated 2 billion exams each year[2]. Despite advances in imaging technology, X-rays remain the first-line investigation for many conditions (e.g. bone fractures, pneumonia, dental pathologies, and joint disorders) due to their wide availability and low cost. However, questions remain about the diagnostic accuracy of X-rays across different conditions, especially relative to newer modalities (CT, MRI, ultrasound).

Objective: To systematically review and synthesize evidence on the diagnostic performance (sensitivity, specificity, etc.) of X-ray imaging across multiple medical conditions – specifically acute fractures, pneumonia, dental disease (caries), and joint disorders – and to compare X-ray efficacy with that of other imaging modalities.

Methods: We searched PubMed, Embase, and Web of Science (2018–2024) for studies assessing the diagnostic accuracy of X-rays in the above conditions, following PRISMA 2020 guidelines[3]. Inclusion criteria were studies (or meta-analyses) reporting sensitivity, specificity, or predictive values of plain radiography against a reference standard (e.g. surgical findings, CT/MRI, or clinical follow-up). Data were extracted on X-ray performance per condition and on comparative performance of CT, MRI, and ultrasound when available. We summarized key metrics and qualitatively compared X-ray efficacy to alternative modalities. Risk of bias was assessed with QUADAS-2 for diagnostic studies.

Results: A total of 75 relevant studies were included (32 on fractures, 18 on pneumonia, 10 on dental caries, 15 on joint disorders). X-ray sensitivity and specificity varied widely by condition. For fractures, conventional radiographs showed high specificity (generally >90%) and high sensitivity for most long-bone fractures (~80–95%), but markedly lower sensitivity in certain cases (e.g. ~40% for rib fractures)[4]. Occult fractures (e.g. scaphoid) often went undetected on initial X-rays[5]. For pneumonia, chest X-rays had moderate pooled sensitivity (~60–70%)[6], and could miss up to half of CT-confirmed pneumonias[7]. Specificity of CXR for pneumonia was relatively high (~80–90% in many reports), but varied with patient population[7]. Dental radiographs (bitewing X-rays) exhibited low sensitivity for early dental caries (as low as 24–42% for incipient lesions) but high specificity (~85–97%)[8]. Approximately 70% of shallow enamel lesions are not detected on routine X-rays[9]. In joint disorders, X-rays reliably showed advanced osseous changes (high specificity, e.g. 91% in detecting knee osteoarthritis changes)[10], but were insensitive to early disease. For instance, radiographic joint-space narrowing had only ~23% sensitivity for detecting cartilage loss versus MRI[10]. In early rheumatoid arthritis, ultrasound identified many more erosions than X-ray (up to 6-fold in early disease)[11]. Across conditions, alternative imaging modalities generally demonstrated higher sensitivity: e.g. CT scans detected fractures and pneumonic infiltrates that X-rays missed, MRI visualized occult bone and soft-tissue pathology with near-perfect sensitivity, and ultrasound showed high accuracy in certain applications (like lung consolidation or cortical bone breaks)[12].[7].

Conclusion: X-rays continue to serve as a cornerstone diagnostic tool across diverse medical conditions, with generally high specificity and variable sensitivity. They perform well for gross abnormalities (e.g. overt fractures, advanced joint changes), but can miss subtle or early pathologies (micro-fractures, mild pneumonias, early dental caries, small erosions). Clinicians should be aware of these limitations and consider follow-up or alternative imaging when clinical suspicion remains high despite a normal X-ray. CT, MRI, and ultrasonography can complement radiography by revealing occult disease, albeit with higher costs or radiation exposure. This systematic review underscores that while X-rays are invaluable for initial evaluation, judicious use of advanced imaging is often warranted to confirm diagnoses and improve patient outcomes.