Limitations
We reviewed the information provided by all clinical trials focused on
HQ and chloroquine for patients diagnosed with COVID-19 available in the
WHO-ICTRP database until April 8th, 2020, at 10:30
GMT-6. We chose the WHO-ICTRP because it compiles data from
ClinicalTrials.gov and 10 primary registers
(https://www.who.int/ictrp/en/). In the scenario of the COVID-19
pandemic, we judged that this approach would provide an improved
overview of clinical trials being planned in different countries.
Nevertheless, as we did not search the primary registers directly, it is
possible that some potentially eligible registered RCTs could have been
missed. Also, the data analyzed in this study is limited to the
information provided in the record of the clinical trials’ register. A
minority of the clinical trials provided access to the full study
protocol; therefore, the data collected and analyzed in this study may
be incomplete if authors have deliberately left information missing on
the publicly available record of the planned trials. Nevertheless, if
the trial registers are incomplete for low quality designs or deliberate
actions, this represents a risk to the strength of the evidence that
will ultimately be available to inform decisions. Finally, as the
development of research on COVID-19 is evolving fast, additional RCTs
may exist which were planned but registered after the study timeline;
these trials were not included in the present analysis.