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Pilot implementation of Short Message Service for randomisation in a multisite pragmatic factorial clinical trial in Kenya

Published onJun 16, 2023
Pilot implementation of Short Message Service for randomisation in a multisite pragmatic factorial clinical trial in Kenya


The traditional use of sealed envelopes for randomisation is susceptible to manipulation and the risk of damage to envelopes in transit.  Additionally, the filling and sealing envelopes is, tedious, time-consuming, and error-prone. Other randomisation alternatives such as web-based methods are preferred. However, they are expensive and unsuitable in low resource settings. Mobile phone-based randomisation using Short Message Service (SMS) potentially offers a low-cost and reliable alternative.


We developed an SMS-based system for random allocation of treatments. It’s a three-tier system consisting of a data , business logic and administration  interfaces. An Android app and plain text messaging were used to formulate text messages using a predefined syntax  . The logic layer verified the input parameters and obtained an allocation from the data layer before returning a response to the sender. The text response contained the details of the treatment allocation. The administrative interface summarized randomisation transactions, allowed  SMS monitoring, managed users and uploaded the randomisation sequence. The study was done in two sites of a multi-site factorial clinical trial in Kenya involving two interventions with up to nine possible allocations. We evaluated the accuracy of treatment allocations against the master randomisation list for each randomisation message processed, and SMS latency in seconds. A post-implementation survey was used to evaluate user feedback.


A total of 219 participants were randomised between 7th February 2022 and 11th April 2022, out of which 180 were randomised to the first pair of treatments while 39 were randomised to both pairs of treatment. Allocation accuracy was 100%. Median latency was 21 seconds with the fastest message processed in 10 seconds and the slowest (non-network delayed) message processed in 2129 seconds. Four users completed a qualitative survey, three of whom preferred using the Android app over plain SMS, while all users indicated preference for SMS randomisation over sealed envelopes.


The pilot study demonstrated that SMS is a feasible approach to randomisation for large clinical trials. The framework developed from this work will guide future study implementation  and provide a reliable and low-cost platform to support  clinical trials in low-resource settings.

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