Clinical and radiologic characteristics of radiologically missed miliary tuberculosis

Abstract

While chest CT provides important clue for diagnosis of miliary tuberculosis (TB), patients are occasionally missed on initial CT, which might delay the diagnosis. This study was to evaluate the clinical and radiological characteristics of radiologically missed miliary TB.Total 117 adult patients with microbiologically confirmed miliary TB in an intermediate TB-burden country were included. 'Missed miliary TB' were defined as the case in which miliary TB was not mentioned as a differential diagnosis in the initial CT reading. Clinical characteristics and radiologic findings including the predominant nodule size, demarcation of miliary nodules and disease extent on CT were retrospectively evaluated. Findings were compared between the missed and non-missed miliary TB groups. Multivariable analyses were performed to determine independent risk factors of missed miliary TB.Of 117 patients with miliary TB, 13 (11.1%) were classified as missed miliary TB; these patients were significantly older than those with non-missed miliary TB (median age, 71 vs 57 years, P = .024). There was a significant diagnostic delay in the missed miliary TB group (P < .001). On chest CT, patients with missed miliary TB had a higher prevalence of ill-defined nodules (84.6% vs 14.4%; P < .001), miliary nodule less than 2 mm showing granular appearance (69.2% vs 12.5%; P < .001), and subtle disease extent (less than 25% of whole lung field, 46.2% vs 8.7%; P < .001). Multivariable analysis revealed that only CT findings including ill-defined nodule (Odd ratios [OR], 15.64; P = .002) and miliary nodule less than 2 mm (OR, 10.08; P = .007) were independently associated with missed miliary TB.Approximately 10% of miliary TB could be missed on initial chest CT, resulting in a delayed diagnosis and treatment. Caution is required in patients with less typical CT findings showing ill-defined miliary nodules less than 2 mm showing granular appearance and follow-up CT might have a benefit.

Figure 1

Flow chart of the study inclusion. ICD-10 = 2019 international classification of diseases-10 diagnosis code; TB = tuberculosis; CT = computed tomography.

Figure 2

Example of CT interpretation of miliary nodules. (a) Miliary nodule with well-defined nodules measuring 2−4 mm and showing random distribution on axial high-resolution CT. (b) Miliary nodule with ill-defined miliary nodules measuring less than 2 mm showing coarse and granular appearance on axial high-resolution CT.

Figure 3

73-year-old woman with missed miliary TB. (a) Miliary TB in a 73-year-old woman admitted to hospital with persistent fever and underlying diffuse large B-cell lymphoma with ongoing chemotherapy. A lung window of an axial CT (1.0 mm section thickness) shows fine, ill-defined nodules predominantly < 2 mm in size and showing a coarse, granular appearance distributed throughout both lungs, with ill-defined, patchy ground glass opacities. A calcified granuloma is shown in right upper lobe, possible a sequelae of previous tuberculosis (arrow). Miliary TB was missed on the initial CT reading at symptom onset. The CT was interpreted as an atypical pathogen pneumonia, such as viral pneumonia or a drug reaction. (b) 8-mm axial maximum intensity projection (MIP) slab shows non-classic miliary nodules superimposed on same level of image, which is more conspicuous on MIP slab.

Figure 4

67-year-old woman with missed miliary TB. Miliary TB in a 67-year-old woman who was admitted to hospital with persistent fever. (a) A lung window of an axial CT (1.0 mm section thickness) shows irregular mass-like consolidation in the right lower lobe superior segment and surrounding centrilobular nodules with branching opacities, showing tree-in-bud appearance (arrow). (b) A lung window of a coronal CT (5 mm section thickness) shows multiple well-defined randomly distributed micronodules, predominantly 2−4 mm in size, in both lungs. Miliary TB was missed on the initial CT reading at symptom onset. Mass-like consolidation in the right lower lobe was misinterpreted as a primary lung cancer, and miliary nodules were interpreted as metastasis. Centrilobular nodules with tree-in-bud appearance located in locations typical of secondary TB were neglected and not interpreted appropriately.