Abstract
BackgroundStudies measuring contact networks have helped to improve our understanding of infectious disease transmission. However, several methodological issues are still unresolved, such as which method of contact measurement is the most valid. Further, complete network analysis requires data from most, ideally all, members of a network and, to achieve this, acceptance of the measurement method. We aimed at investigating measurement error by comparing two methods of contact measurement – paper diaries vs. wearable proximity sensors – that were applied concurrently to the same population, and we measured acceptability.MethodsWe investigated the contact network of one day of an epidemiology conference in September 2014. Seventy-six participants wore proximity sensors throughout the day while concurrently recording their contacts with other study participants in a paper-diary; they also reported on method acceptability.ResultsThere were 329 contact reports in the paper diaries, corresponding to 199 contacts, of which 130 were noted by both parties. The sensors recorded 316 contacts, which would have resulted in 632 contact reports if there had been perfect concordance in recording. We estimated the probabilities that a contact was reported in a diary as: P = 72 % for <5 min contact duration (significantly lower than the following, p < 0.05), P = 86 % for 5-15 min, P = 89 % for 15-60 min, and P = 94 % for >60 min. The sets of sensor-measured and self-reported contacts had a large intersection, but neither was a subset of the other. Participants’ aggregated contact duration was mostly substantially longer in the diary data than in the sensor data. Twenty percent of respondents (>1 reported contact) stated that filling in the diary was too much work, 25 % of respondents reported difficulties in remembering contacts, and 93 % were comfortable having their conference contacts measured by sensors.ConclusionReporting and recording were not complete; reporting was particularly incomplete for contacts <5 min. The types of contact that both methods are capable of detecting are partly different. Participants appear to have overestimated the duration of their contacts. Conducting a study with diaries or wearable sensors was acceptable to and mostly easily done by participants. Both methods can be applied meaningfully if their specific limitations are considered and incompleteness is accounted for.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1676-y) contains supplementary material, which is available to authorized users.
Highlights
Studies measuring contact networks have helped to improve our understanding of infectious disease transmission
Data collection Wearable sensors We used active Radio Frequency Identification (RFID) sensors developed by the SocioPatterns collaboration; a precise description of the devices’ functionality has been published [15], which we briefly summarise here: Participants wore the sensors in a pouch that was attached to a lanyard; the sensors exchange low-power radio signals only on short distance (~1.5 m) if unobstructed [15], e.g., not covered by hands, and can thereby detect closeproximity face-to-face events between participants; detected interaction events are sent to and logged by radio receivers; the final data is aggregated with a temporal resolution of 20 seconds
We report the results for the most basic correction, R0,het = R0,hom∙(1 + CV2) - with CV being the coefficient of variation of the degree and the indices hom and het indicating R0 assuming a homogeneous degree and R0 corrected for degree heterogeneity, respectively [28, 29] to determine how R0 differs from the homogeneous mixing model, when we allow for degree dispersion
Summary
Studies measuring contact networks have helped to improve our understanding of infectious disease transmission. Various methods have been developed to measure social mixing [4], in particular contact diaries [5,6,7,8], wearable sensors [9,10,11,12,13,14,15,16], and video analyses [17] These methods are heavily used to parameterize models that inform public health policy [7, 18] and support contact tracing [19]. Some robust features have emerged from these studies: in particular, that reporting of transient contacts is poor whereas extended contacts are reported reliably [20,21,22]. More studies are needed, especially for contacts occurring in different contexts
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