There has been a backlog in the testing of samples for Covid-19 by public laboratories in the past few weeks, the National Institute for Communicable Diseases said.

The NICD, in its report summarising the national laboratory testing for SARS-Cov2 (the virus causing Covid-19) for the period up to May 23, said the delays in laboratory testing affected the analysis of the testing data and the identification of outbreak hotspots.

The NICD said the number of days it takes for the collection of a sample and reporting of results in the public sector increased from 2.5 days to eight days, from week 17 to week 21, as a result of laboratory testing backlogs.

This while the turnaround times in the private sector remained around two days.

The NICD said among the tests conducted in the public sector, the increased turnaround time has been observed in all five provinces where the largest number of tests have been conducted. The provinces are Gauteng, Western Cape, KwaZulu-Natal, Eastern Cape and Free State.

"However, the largest delay in testing has been observed in Gauteng from four days in week 17 to [about] 10 days in week 21."

It said testing for SARS-CoV2 began on January 28 at the NICD.

After the first case in SA was confirmed on March 5, testing was expanded to a larger network of private and National Health Laboratory Services laboratories.

The NICD said from March 1 to May 23, 564,155 laboratory tests for SARS-CoV2 were done nationally.

The public sector laboratories conducted 297,977 tests, with 4.5% testing positive. Over the same period, private sector laboratories conducted 266,178 tests, with 4% testing positive.

The NICD said the number of tests increased week on week to week 19. It said testing decreased on the week of May 10 to 16 (week 20) and the week of May 17 to 23 (week 21).

"The decrease in the last two weeks is likely due to a limited supply of testing kits. In addition, due to backlogs in laboratory testing, all tests for samples collected in week 21 may not yet be reflected."

The NICD said in week 21, Western Cape, Gauteng and KwaZulu-Natal continued to perform the largest number of tests.

The NICD said the backlog in testing of samples by public laboratories will affect the reported numbers of tests performed.

"The delays in laboratory testing affects the analysis of the testing data and the identification of outbreak hotspots."