New ICMR plan for states to ex­pand an­ti­body tests

Hindustan Times (Jalandhar) - - HTSPOTLIGH­T - Rhythma Kaul let­ters@hin­dus­tan­ n

Pe­ri­odic sero-sur­veys are nec­es­sary to es­tab­lish a trend and the states have been asked to take it for­ know dis­ease preva­lence


NEWDELHI:Af­ter com­plet­ing a pi­lot sero-sur­vey (a test of the blood serum of a group of in­di­vid­u­als) last week to check the level of ex­po­sure to the Sars-CoV-2 virus that causes Covid-19 in the com­mu­nity us­ing Elisa-based an­ti­body test­ing, the In­dian Council of Med­i­cal Re­search’s (ICMR) on Satur­day sent an ad­vi­sory to all states to ex­pand the sur­vey.

ICMR has pre­pared a com­pre­hen­sive list of cat­e­gories of peo­ple who should be tested as part of the sur­vey, in­clud­ing high-risk or vul­ner­a­ble pop­u­la­tions (health­care work­ers, front­line work­ers, im­mune-com­pro­mised in­di­vid­u­als, in­di­vid­u­als in con­tain­ment zones, se­cu­rity staff, pris­on­ers) to know who has been in­fected in the past and has now re­cov­ered.

“ICMR con­ducted the pi­lot sur­vey to get a ba­sic sense of how In­dia is in terms of dis­ease spread cur­rently, for which the re­sults should be out in some time. How­ever, pe­ri­odic sero-sur­veys are nec­es­sary to es­tab­lish a trend and the states have been asked to take it for­ward and keep do­ing it pe­ri­od­i­cally to know the preva­lence of the dis­ease at ground level,” said a se­nior ICMR of­fi­cial, who did not wish to be iden­ti­fied.

The blood sam­ples will be tested for de­tect­ing IgG an­ti­bod­ies us­ing the Elisa method (IgG is an an­ti­body that de­vel­ops later as com­pared to the other an­ti­bod­ies, hence, de­ter­mines a past in­fecde­vel­oped tion).

For sev­eral vi­ral in­fec­tions, an­ti­body tests are use­ful for dis­ease de­tec­tion af­ter 5–7 days of ill­ness. Un­der­stand­ing re­lated to an­ti­body tests for Covid-19 is evolv­ing and sev­eral tests are be­ing de­vel­oped glob­ally. The IgG an­ti­bod­ies gen­er­ally start ap­pear­ing af­ter two weeks of the on­set of in­fec­tion, once the in­di­vid­ual has re­cov­ered af­ter in­fec­tion and last for sev­eral months. The IgG test is not use­ful for de­tect­ing acute in­fec­tion but in­di­cates episodes of Sars-CoV-2 in­fec­tion in the past, say ex­perts.

“Sero-sur­veys help to un­der­stand the pro­por­tion of pop­u­la­tion ex­posed to Sars-CoV-2 in­fec­tion in­clud­ing asymp­to­matic in­di­vid­u­als. De­pend­ing upon the level of sero-preva­lence of in­fec­tion, ap­pro­pri­ate pub­lic health in­ter­ven­tions can be planned and im­ple­mented for pre­ven­tion and con­trol of the dis­ease. Pe­ri­odic sero-sur­veys are use­ful to guide the pol­icy mak­ers,” said ICMR in a state­ment.

Sci­en­tists at ICMR-Na­tional In­sti­tute of Virol­ogy, Pune have and val­i­dated an indige­nous IgG Elisa test for an­ti­body de­tec­tion for Sars-CoV-2.

The test has un­der­gone in­tense val­i­da­tion in three stages and has been found to have high sen­si­tiv­ity and speci­ficity. To fast-track pro­duc­tion of the IgG Elisa test, ICMR has trans­ferred this tech­nol­ogy to many pharma com­pa­nies such as Zy­dus Cadila, J Mi­tra & Com­pany, Meril Di­ag­nos­tics, Vox­tur Bio, Triv­it­ron Health­care, Kar­wah En­ter­prises and Ave­con Health­care.

“The tech­nol­ogy has been trans­ferred to var­i­ous en­ti­ties with­out ex­clu­siv­ity clause and there­fore can be fur­ther shared with oth­ers as per de­mand and ca­pa­bil­ity. ICMR has of­fered to pro­vide tech­ni­cal sup­port to States/ UTs, if re­quired, in plan­ning and car­ry­ing out sero-sur­veys us­ing IgG Elisa test kits and also in­ter­pret­ing the re­sults,” said the re­search body.

Ex­perts on in­fec­tious dis­eases, how­ever, feel that merely know­ing whether the pop­u­la­tion has de­vel­oped an­ti­bod­ies against the virus is not enough.

“Merely know­ing the vol­ume of peo­ple who have been in­fected will only pro­vide the sense of the spread of the dis­ease; what we must try to know is the quan­tity and qual­ity of an­ti­bod­ies be­ing pro­duced against the virus. Also, for how long th­ese an­ti­bod­ies stay in hu­man blood so as to know if it’s enough to of­fer pro­tec­tion,” says Dr Lalit Kant, for­mer head of epi­demi­ol­ogy divi­sion at ICMR

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