Predictive value of pulse oximetry for mortality in infants and children presenting to primary care with clinical pneumonia in rural Malawi: A data linkage study.

Background The mortality impact of pulse oximetry use during infant and childhood pneumonia management at the primary healthcare level in low-income countries is unknown. We sought to determine mortality outcomes of infants and children diagnosed and referred using clinical guidelines with or without pulse oximetry in Malawi. Methods and findings We conducted a data linkage study of prospective health facility and community case and mortality data. We matched prospectively collected community health worker (CHW) and health centre (HC) outpatient data to prospectively collected hospital and community-based mortality surveillance outcome data, including episodes followed up to and deaths within 30 days of pneumonia diagnosis amongst children 0-59 months old. All data were collected in Lilongwe and Mchinji districts, Malawi, from January 2012 to June 2014. We determined differences in mortality rates using <90% and <93% oxygen saturation (SpO(2)) thresholds and World Health Organization (WHO) and Malawi clinical guidelines for referral. We used unadjusted and adjusted (for age, sex, respiratory rate, and, in analyses of HC data only, Weight for Age Z-score [WAZ]) regression to account for interaction between SpO(2) threshold (pulse oximetry) and clinical guidelines, clustering by child, and CHW or HC catchment area. We matched CHW and HC outpatient data to hospital inpatient records to explore roles of pulse oximetry and clinical guidelines on hospital attendance after referral. From 7,358 CHW and 6,546 HC pneumonia episodes, we linked 417 CHW and 695 HC pneumonia episodes to 30-day mortality outcomes: 16 (3.8%) CHW and 13 (1.9%) HC patients died. SpO(2) thresholds of <90% and <93% identified 1 (6%) of the 16 CHW deaths that were unidentified by integrated community case management (iCCM) WHO referral protocol and 3 (23%) and 4 (31%) of the 13 HC deaths, respectively, that were unidentified by the integrated management of childhood illness (IMCI) WHO protocol. Malawi IMCI referral protocol, which differs from WHO protocol at the HC level and includes chest indrawing, identified all but one of these deaths. SpO(2) < 90% predicted death independently of WHO danger signs compared with SpO(2) >= 90%: HC Risk Ratio (RR), 9.37 (95% CI: 2.17-40.4, p = 0.003); CHW RR, 6.85 (1.15-40.9, p = 0.035). SpO(2) < 93% was also predictive versus SpO(2) >= 93% at HC level: RR, 6.68 (1.52-29.4, p = 0.012). Hospital referrals and outpatient episodes with referral decision indications were associated with mortality. A substantial proportion of those referred were not found admitted in the inpatients within 7 days of referral advice. All 12 deaths in 73 hospitalised children occurred within 24 hours of arrival in the hospital, which highlights delay in appropriate care seeking. The main limitation of our study was our ability to only match 6% of CHW episodes and 11% of HC episodes to mortality outcome data. Conclusions Pulse oximetry identified fatal pneumonia episodes at HCs in Malawi that would otherwise have been missed by WHO referral guidelines alone. Our findings suggest that pulse oximetry could be beneficial in supplementing clinical signs to identify children with pneumonia at high risk of mortality in the outpatient setting in health centres for referral to a hospital for appropriate management. Author summary Why was this study done? Pneumonia is a leading cause of death of children under 5 years old, and early identification and treatment of severe cases is required to prevent deaths. Pulse oximetry is more sensitive at detecting hypoxaemia than clinical signs alone and therefore can potentially prevent more deaths from pneumonia. There is a lack of evidence of the effect on child deaths of pulse oximetry use by healthcare workers in informal community settings and at formal primary care clinics, and this study sought to fill this evidence gap. What did the researchers do and find? We linked Malawian community health worker and health centre outpatient data to hospital and community mortality data to determine the mortality outcomes for children with pneumonia identified by pulse oximetry or clinical signs or both as outpatients. We show that pulse oximetry identified fatal episodes of childhood pneumonia that did not have identified clinical signs. Pulse oximetry readings of less than 90% oxygen saturation (SpO2) identified 6% of deaths at community health worker level (1/16) and 23% of deaths at health centre level (3/13) not identified by clinical signs. Increasing the threshold to less than 93% SpO2, pulse oximetry identified 1 additional death (1/13, 7.7% of deaths) not identified by clinical signs at the health centre level only. All of the health centre deaths identified by pulse oximetry except one were also identified by chest indrawing in this high-mortality setting. What do these findings mean? Our findings suggest that pulse oximetry could be beneficial in supplementing clinical signs to identify children with pneumonia at high risk of mortality in the outpatient setting in health centres for referral to a hospital for appropriate management. In high-mortality settings in low- and middle-income countries, in the absence of pulse oximetry, presence of chest indrawing could potentially be explored as a referral sign to a hospital but needs further research in routine settings.