These consolidated petitions for review on certiorari assail the Decision^[1] dated February 3, 2006 of the Court of Appeals in CA-G.R. SP No. 74399, which reversed and set aside the Decision^[2] dated September 6, 2002 of the Employees' Compensation Commission (ECC) in ECC Case No. GM-12987-202 and granted respondent Maria Teresa S.A. Cordero's claim for compensation benefits under Presidential Decree No. 626 (P.D. No. 626),^[3] as amended.

The antecedent facts are as follows:

From October 1987, Cordero occupied several contractual and casual positions in the Government Service Insurance System (GSIS) until she was extended a permanent appointment on May 7, 1990. On December 10, 1996, she was promoted as Senior General Insurance Specialist,^[4] her position to date.

In her post, Cordero examines insured government properties to verify the existence of overinsurance or underinsurance, the degree of risks, correctness of rate charged and paying capacity of the insurer; gathers situations and conditions of insurance risks exposure and rates, previous losses and other pertinent data and information relative to non-life insurance; inspects damaged properties and reports the value of a claim payable to the insured, in accordance with established policies in force; and interviews or corresponds with claimants and witnesses to determine the extent of GSIS' liability for insurance claims.^[5]

From April 12 to 17, 2000, Cordero was confined at the Quezon City Medical Center and was diagnosed with Chronic Glomerulonephritis with Hypertension. Then, from June 25 to 28, 2001 and from October 10 to 14, 2001, she was confined at St. Luke's Medical Center in Quezon City. The final diagnosis was Chronic Renal Failure secondary to Chronic Glomerulonephritis. Also, based on her medical records, she had hypertension since 1995.^[6]

Accordingly, Cordero filed with the GSIS a claim for compensation benefits under P.D. No. 626, as amended. She stated that in her pre-employment physical and medical examinations, she was in perfect health when she entered GSIS in 1987. But later, she was diagnosed with hypertension, and then hospitalized in April 2000, June 2001 and October 2001 because of Chronic Renal Failure secondary to Chronic Glomerulonephritis.

To prove that her illness is work-connected, she presented a medical certificate^[7] dated December 6, 2001 issued by Dr. Florencio J. Pine, M.D., F.P.C.P., F.P.S.N., Internal Medicine, Kidney Diseases and Hypertension of the UERM Memorial Hospital and National Kidney Institute. Dr. Pine certified that based on the history and available diagnostic examinations, the predominant evidence indicates that Cordero's end stage renal disease is secondary to the combined damage inflicted by the urinary tract infection and hypertension since 1995. He likewise certified that both conditions are work-related.

Cordero also presented a Certification^[8] issued by Mr. Arnulfo Q. Canivel, Division Chief III, GSIS Claims Department, stating that "[t]he nature of her work and working conditions outside the office increased the risk and is probably a big factor in the development of her hypertension which led to her End Stage Renal Disease secondary to Chronic Gl[o]merulonephritis requiring three times a week hemodialysis."

On January 16, 2002, the GSIS denied her claim on the ground that her illness is not work-connected and her duties did not increase the risk of contracting the same.^[9] Cordero sought reconsideration, but to no avail. Aggrieved, Cordero appealed to the ECC.

On September 6, 2002, the ECC affirmed the Decision of the GSIS and held that:

x x x x

As Sr. General Insurance Specialist, there was no proof that she was significantly exposed to occupational hazards that would result to kidney injury. Her job does not involve exposure to chemicals implicated in Chronic Glomerulonephritis. Thus, the ailment cannot be considered work-related.

WHEREFORE, the assailed decision is hereby AFFIRMED and the instant appeal is dismissed for lack of merit.

SO ORDERED.^[10]

Pursuant to Rule 43^[11] of the Rules of Court, Cordero filed a petition for review with the Court of Appeals. In its Decision dated February 3, 2006, the Court of Appeals reversed the ECC ruling and held that Cordero contracted Chronic Glomerulonephritis during her employment in the GSIS and that the risk of contracting the same was increased by her working conditions. It pointed out that in her pre-employment physical and medical examination with the GSIS in 1987, Cordero was in perfect health condition. But sometime in 1995, she was diagnosed with hypertension, which eventually led to the development of her End Stage Renal Disease secondary to Chronic Glomerulonephritis. The Court of Appeals agreed with her physician that both conditions are work-related. The fallo of the decision reads:

WHEREFORE, premises considered, the Petition for Review is GRANTED DUE COURSE. The Decision of the Employees' Compensation Commission in ECC Case No. GM-12987-202 approved on 06 September 2002 under Board Resolution No. 02-09-646, is REVERSED and SET ASIDE and the Government Service Insurance System is hereby DIRECTED to pay petitioner Maria Teresa S.A. Cordero her claim for compensation benefits pursuant to P.D. 626, as amended. No costs.

SO ORDERED.^[12]

Hence these petitions. Petitioner GSIS raises the following issues:

I.

WHETHER THE RESPONDENT'S AILMENT DENOMINATED AS "CHRONIC GLOMERULONEPHRITIS" MAY BE CONSIDERED WORK-CONNECTED PURSUANT TO SECTION 1 (B), RULE III OF THE AMENDED RULES OF P.D. NO. 626, AS AMENDED.

II.
WHETHER THE COURT OF APPEALS WAS CORRECT IN ALLOWING THE RESPONDENT'S CLAIM FOR COMPENSATION BENEFITS UNDER P.D. 626, AS AMENDED, MAINLY DUE TO A HUMANITARIAN IMPULSE.^[13]

Petitioner ECC, for its part, raises a single issue:

[WHETHER] THE COURT OF APPEALS ERRED IN CONSIDERING CHRONIC GLOMERULONEPHRITIS AS A WORK-RELATED DISEASE AND COMPENSABLE UNDER THE THEORY OF "INCREASED RISK."^[14]

In her Memorandum^[15] dated February 22, 2007, covering both G.R. No. 171378 and G.R. No. 171388, respondent Cordero presents the following "statement of issues":

1. THAT RESPONDENT WAS ABLE TO DISCHARGE THE BURDEN OF SHOWING THAT THE RISK OF CONTRACTING HER AILMENT, CHRONIC GLOMERULONEPHRITIS, WAS INCREASED BY HER WORKING CONDITIONS, HENCE, COMPENSABLE UNDER THE LAW.
   
   
2. THAT THE COMPENSABILITY OF THE CLAIM IS CONSISTENT WITH APPLICABLE LAWS AND PREVAILING JURISPRUDENCE.
   
   
3. THAT PRESIDENTIAL DECREE 626, AS AMENDED, IS A SOCIAL LEGISLATION THAT MUST BE INTERPRETED AND CONSTRUED IN FAVOR OF ITS INTENDED BENEFICIARIES.^[16]

Simply stated, the issue posed for our resolution is: Is respondent's End Stage Renal Disease secondary to Chronic Glomerulonephritis compensable under P.D. No. 626, as amended?

GSIS contends that Chronic Glomerulonephritis is not an occupational disease; accordingly, Cordero should adduce proof that the risk of contracting her disease was increased by her working conditions. But Cordero failed to do so; hence, her illness is not compensable under the law.

Cordero counters that her illness is compensable even if Chronic Glomerulonephritis is not an occupational disease because her working conditions increased the risk of contracting the illness. She contends that she started with the GSIS in perfect health but years later, because of the strenuous nature of her work, she suffered from hypertension, which eventually led to the damage of her kidney resulting to End Stage Renal Disease.

After a careful consideration of the submissions of the parties, we are unanimous in finding that Cordero has substantially proved her claim to compensability.

Under Section 1(b),^[17] Rule III implementing P.D. No. 626, sickness or death is compensable if the cause is included in the list of occupational diseases annexed to the Rules. If not so listed, compensation may still be recovered if the illness is caused or precipitated by factors inherent in the employee's work and working conditions.^[18] Here, strict rules of evidence are not applicable since the quantum of evidence required under P.D. No. 626 is merely substantial evidence, which means "such relevant evidence as a reasonable mind might accept as adequate to support a conclusion."^[19]

What the law requires is a reasonable work-connection and not a direct causal relation.^[20] It is sufficient that the hypothesis on which the workmen's claim is based is probable since probability, not certainty, is the touchstone.^[21]

Inasmuch as Cordero's disease was not listed as an occupational disease, it is incumbent upon her to adduce substantial proof that would show that the nature of her employment or working conditions increased the risk of End Stage Renal Disease or Chronic Glomerulonephritis. The evidence presented by Cordero shows that her Chronic Glomerulonephritis that led to End Stage Renal Disease was caused by hypertension.^[22]

At the onset, Cordero was given a clean bill of health and declared fit-to-work when she was employed by GSIS in 1987. But in 1995, she contracted hypertension. While End Stage Renal Disease secondary to Chronic Glomerulonephritis is not among those enumerated as an Occupational Disease under Annex "A" of the ECC Rules,^[23] it is scientifically linked to hypertension, a compensable illness.^[24] Hence, we cannot close our eyes to the reasonable connection of her work vis-à-vis her ailment.

Years after Cordero contracted hypertension, her health condition worsened when she was hospitalized in April 2000, June 2001 and October 2001 and she was diagnosed as having End Stage Renal Disease secondary to Chronic Glomerulonephritis. Her attending physician certified that based on medical examinations, her hypertension has led to the development of her End Stage Renal Disease. In our jurisprudence, a doctor's certification as to the nature of the claimant's disability normally deserves full credence because in the normal course of things, no medical practitioner will issue certifications indiscriminately, considering the serious and far-reaching effects of false certifications and its implications upon his own interests as a professional.^[25]

Premised on the aforementioned considerations, this Court affirms the findings and conclusions reached by the Court of Appeals upholding Cordero's claim to compensability.

WHEREFORE, the instant petitions are DENIED. The Decision dated February 3, 2006 of the Court of Appeals in CA-G.R. SP No. 74399 is hereby AFFIRMED. Petitioner Government Service Insurance System is hereby ORDERED to pay respondent Maria Teresa S.A. Cordero the compensation benefits due her under Presidential Decree No. 626, as amended.

SO ORDERED.

Carpio Morales, Velasco, Jr., Leonardo-De Castro^*, and Brion, JJ., concur.

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* Designated member of Second Division pursuant to Special Order No. 586 in place of Associate Justice Antonio Eduardo B. Nachura, who was earlier designated as an additional member per Special Order No. 571 but will take no part being then the Solicitor General.

^[1] Rollo (G.R. No. 171378), pp. 70-81. Penned by Associate Justice Celia C. Librea-Leagogo, with Associate Justices Renato C. Dacudao and Lucas P. Bersamin concurring.

^[2] Id. at 82-84.

^[3] FURTHER AMENDING CERTAIN ARTICLES OF PRESIDENTIAL DECREE NO. 442 ENTITLED "LABOR CODE OF THE PHILIPPINES," done on December 27, 1974 and took effect on January 1, 1975.

^[4] Rollo (G.R. No. 171378), p. 71.

^[5] Records, p. 26.

^[6] Rollo (G.R. No. 171378), p. 83.

^[7] Records, p. 28.

^[8] Id. at 41.

^[9] Id. at 8.

^[10] Rollo (G.R. No. 171378), p. 84.

^[11] APPEALS FROM THE COURT OF TAX APPEALS AND QUASI-JUDICIAL AGENCIES TO THE COURT OF APPEALS.

^[12] Rollo (G.R. No. 171378), p. 80.

^[13] Id. at 51.

^[14] Rollo (G.R. No. 171388), p. 15.

^[15] Rollo (G.R. No. 171378), pp. 235-265.

^[16] Id. at 243-244.

^[17] SECTION 1. Grounds. - . . .

(b) For the sickness and the resulting disability or death to be compensable, the sickness must be the result of an occupational disease listed under Annex "A" of these Rules with the conditions set therein satisfied, otherwise, proof must be shown that the risk of contracting the disease is increased by the working conditions.

x x x x

^[18] Jacang v. Employees' Compensation Commission, G.R. No. 151893, October 20, 2005, 473 SCRA 520, 525-526.

^[19] Castor-Garupa v. Employees' Compensation Commission, G.R. No. 158268, April 12, 2006, 487 SCRA 171, 180.

^[20] Salalima v. Employees' Compensation Commission, G.R. No. 146360, May 20, 2004, 428 SCRA 715, 723.

^[21] Limbo v. Employees' Compensation Commission, 434 Phil. 703, 707 (2002).

^[22] Castor-Garupa v. Employees' Compensation Commission, supra note 19.

^[23] Id. at 179.

^[24] Republic v. Mariano, G.R. No. 139455, March 28, 2003, 400 SCRA 86, 92-93.

^[25] Ijares v. Court of Appeals, G.R. No. 105854, August 26, 1999, 313 SCRA 141, 151-152.