Objective A biphasic waveform pattern in coagulation assays has been shown to correlate with the onset of disseminated intravascular coagulation in adult patients. The aim of this study was to ascertain whether abnormal activated partial thromboplastin time (aPTT) waveforms are present in children with meningococcal septicaemia.

Method Biphasic profiles occur when light transmission decreases before clot formation. To quantitate, light transmission at time 0 is set at 100% and the value at 18 s (TL18) is the index of the abnormality. aPTT waveform analysis was carried out on plasma samples from 56 children: 22 with confirmed meningococcal disease (MCD); 14 with a presumed viral illness inducing a non-blanching rash and 20 healthy children attending for routine surgery.

Results There was a significant difference in aPTT waveform between children with MCD, those with a viral illness (Mann–Whitney U, p<0.0001) and controls (Mann–Whitney U, p<0.0005). There was no significant difference between children with viral illnesses and controls (Mann–Whitney U, p = 0.137). A negative correlation was found between aPTT waveform and length of hospital stay (Spearman rank, r  =  −0.61, p<0.0001); C-reactive protein (Spearman rank, r  =  −0.7, p<0.0001); Glasgow meningococcal septicaemia prognostic score (Spearman rank, r  =  −0.56, p⩽0.01) and paediatric risk of mortality score (Spearman rank, r  =  −0.7, p = 0.0001).

Conclusion These findings demonstrate that the aPTT waveform is abnormal in severe meningococcal sepsis in children when compared with viral illness and controls. aPTT waveform analysis may be a useful tool for the diagnosis of sepsis in children.