Publication:

Revisiting the usefulness of cold agglutinin test and direct Coombs test for bedside diagnosis of paediatric Mycoplasma pneumoniae pneumonia: a prospective observational study

Background Mycoplasma pneumoniae is an important cause of community‑acquired pneumonia in children. Access to specific serological assays is limited in many resource‑constrained settings, necessitating evaluation of simple bedside diagnostic tests such as cold agglutinin test (CAT).

Methods In this prospective observational study, children admitted with radiologically confirmed lobar pneumonia that showed no response to beta-lactams were evaluated with direct Coombs test (DCT) and CAT, and results were compared with Mycoplasma pneumoniae IgM serology as the reference standard. Clinical profile, inflammatory markers, treatment response and outcomes including need for paediatric intensive care and length of hospital stay were also recorded.

Results Among IgM‑positive children, normal total leucocyte counts were significantly more frequent than in IgM‑negative cases, while erythrocyte sedimentation rate was commonly elevated, supporting an atypical pneumonia pattern. DCT showed low sensitivity and poor negative predictive value, whereas CAT demonstrated very high specificity and positive predictive value, making it a useful rule‑in test but unsuitable as a stand‑alone screening tool. CAT positivity was associated with a significantly longer duration of hospital stay, indicating more severe or protracted clinical course among children with demonstrable cold agglutinins.

Conclusions Mycoplasma pneumoniae pneumonia in this cohort was characterized by normal total leucocyte counts with raised erythrocyte sedimentation rate, and CAT emerged as a highly specific rule‑in test, though it could not replace confirmatory serology testing.